composition of modern sand and cretaceous sandstone derived from the sierra nevada california usa with implications for cenozoic and mesozoic uplift and dissection abstract the california sierra nevada represents the roots of a primarily cretaceous magmatic arc that is presently being dissected extensively in the south and to a lesser degree in the north where it is covered by cenozoic volcanic rocks the cenozoic magmatic arc built on top of the cretaceous arc has been dissected concurrently with northward migration of the mendocino triple junction south of which the magmatic arc is inactive a north to south transect from the modern cascade arc along the sierra nevada therefore acts as a proxy for evolution from an active undissected magmatic arc to a transitional arc to a dissected arc to intensely uplifted basement discriminant analysis of cascade and sierra nevada modern alluvial sand defines four compositional groups and clearly distinguishes volcaniclastic undissected arc and plutoniclastic uplifted basement end members two intermediate compositional groups are primarily volcaniplutoniclastic and metamorphiplutoniclastic the former group represents dickinson s 1985 transitional arc the latter represents dissected arc sand composition in the southern sierra nevada reflects significant uplift resulting from a combination of latest cretaceous paleogene uplift and late cenozoic basin and range extension footwall uplift of the western rift shoulder possibly enhanced by mantle lithosphere delamination high concentrations of quartz and feldspar and near absence of aphanitic lithic fragments are typical of the southern sierra nevada and are characteristic of dickinson s basement uplift cretaceous sandstone petrofacies of the great valley group gvg of western california document dissection of the cretaceous magmatic arc as well as erosion of residual orogenic highlands analogous to modern taiwan formed during latest jurassic arc continent collision nevadan orogeny when cretaceous petrofacies data are entered into the modern sand discriminant analysis as unknowns they are classified into the modern cascade sierra nevada groups and a group from taiwan the results confirm that the lowest gvg petrofacies represent erosion of the nevadan suture belt and the undissected post nevadan arc increasing dissection of the arc occurred during the cretaceous but most samples represent transitional arc indicating that even by the latest cretaceous laramide cessation of arc activity in california dissection of the magmatic arc was less than what we see today in the central and southern sierra nevada no cretaceous samples have compositions equivalent to the basement uplift of the southern sierra nevada the application of actualistic sand stone petrofacies in this study provides important constraints on models for the cretaceous to modern history of the sierra nevada as well as implications for arc evolution in general

soil cd cu pb and zn contaminants around mount isa city queensland australia potential sources and risks to human health this article investigates the relationship between soil cd cu pb and zn contaminants and the location and activities of the pb zn ag and cu mines at mount isa queensland australia analysis of the data focuses primarily on soil pb distributions and concentrations because of their potential impact on children s health the xstrata mount isa mines lease xmim is australia s leading emitter of numerous contaminants to the environment including cu and pb and the mining related activities have been linked causally to the findings of a 2008 study that showed 11 3 of local children 12 60 months have blood pb levels 10 g dl queensland government authorities and xstrata mount isa mines pty ltd maintain that contaminants within environmental systems around mount isa are largely the result of near surface mineralization the evidence for whether the contamination is derived from xmim or other possible sources such as the natural weathering of ore rich bedrock is investigated using data from surface and subsurface soil chemistry atmospheric modelling of metal contaminants from mining and smelting operations and local geological and associated geochemical studies sixty surface soil samples collected from sites adjacent to houses parks and schools throughout mount isa city were analyzed for their total extractable cd cu pb and zn concentrations in the 180 m coarser and 180 m finer grain size fractions concentrations in the finer size fraction reveal a range of values cd 0 7 12 5 ppm cu 31 12 100 ppm pb 8 5770 ppm zn 26 11 100 ppm with several samples exceeding australian residential health investigation guidelines spatial analysis shows that surface soil metal concentrations are significantly higher within 2 km of xmim compared to more distant samples and that more than 1000 property lots are at risk of having detrimentally high soil pb levels determination of metal concentrations in 49 samples from eight soil pits shows that surface samples 0 2 cm are enriched significantly relative to those at depth 10 20 cm suggesting an atmospheric depositional origin ausplume air dispersal modelling of pb originating from the cu and pb smelter stacks and mine site fugitive sources confirms that pb is deposited across the urban area during periods of the year not vert similar20 a when the wind blows from the direction of xmim towards the urban area and disperses dusts from the uncovered spoil and road surfaces as well as from stack emission sources although there are some spatially restricted outcrops of pb close to the surface in parts of the urban area the cu ore body is not vert similar244 m below the surface however enriched and significantly correlated surface soil concentrations of cu and pb pearson correlation 0 879 p 0 000 in and around the urban area of mount isa can only be explained by atmospheric transport and deposition of metals from the adjoining mining and smelting operations the results from this study provide unequivocal evidence that both historic and ongoing emissions from xmim are contaminating the urban environment given the ongoing pb poisoning issues in mount isa children it is clear that remediation reductions in mine emissions and more stringent regulatory actions are warranted

natural attenuation of arsenic in the tinto santa rosa acid stream iberian pyritic belt sw spain the role of iron precipitates acid waters and sediments of the tinto santa rosa acid stream iberian pyritic belt sw spain were analysed to determine the role of sedimentary phases in the behaviour of arsenic aqueous arsenic and iron concentrations decreased markedly from the adit mouth to 300 m downstream indicating iron minerals precipitation as well as arsenic sorption onto these newly formed phases this was confirmed by the high arsenic concentrations observed in bed stream precipitates which play a major role in controlling arsenic mobility to unravel the complex nature of the amd sediments a combination of techniques including x ray diffraction xrd scanning electron microscopy sem total solid digestions x ray fluorescence xrf and x ray absorption spectroscopy xas were employed results showed that 1 arsenic was present predominantly in its pentavalent state 2 upstream arsenic was sorbed onto the main phase schwertmannite whereas downstream it was chiefly associated with goethite and jarosite and 3 changes in arsenic speciation with depth were observed in the consolidated terrace sediments where arsenic appeared primarily associated with schwertmannite in the upper part of the terraces but with goethite at depth arsenic mobilization was controlled by sorption onto newly formed precipitates schwertmannite goethite and jarosite causing natural arsenic attenuation

the drenchwater deposit alaska an example of a natural low ph environment resulting from weathering of an undisturbed shale hosted zn pb ag deposit abstract the drenchwater shale hosted zn pb ag deposit and the immediate vicinity on the northern flank of the brooks range in north central alaska is an ideal example of a naturally low ph system the two drainages drenchwater and false wager creeks which bound the deposit differ in their acidity and metal contents moderately acidic waters with elevated concentrations of metals ph 4 3 zn 1400 g l in the drenchwater creek drainage basin are attributed to weathering of an exposed base metal rich massive sulfide occurrence stream sediment and water chemistry data collected from false wager creek suggest that an unexposed base metal sulfide occurrence may account for the lower ph 2 7 3 1 and very metal rich waters up to 2600 g l zn 260 g l cu and 89 g l tl collected at least 2 km upstream of known mineralized exposures these more acidic conditions produce jarosite schwertmannite and fe hydroxides commonly associated with acid mine drainage the high metal concentrations in some water samples from both streams naturally exceed alaska state regulatory limits for freshwater aquatic life affirming the importance of establishing base line conditions in the event of human land development the studies at the drenchwater deposit demonstrate that poor water quality can be generated through entirely natural weathering of base metal occurrences and possibly unmineralized black shale

acid mine drainage at cerro rico de potosi i unabated high strength discharges reflect a five century legacy of mining intensive mining and processing of ag sn pb and zn ores have occurred in various locations within and around the city of potosi bolivia since 1545 surface and subsurface waters stream sediments and soils are contaminated with various ecotoxic metals in the headwaters of the economically vital yet highly impacted upper rio pilcomayo watershed previous studies have documented downstream trace metal contamination however not addressed specific sources the amd discharges identified in this study help link downstream pollution to primary origins the majority of amd would be considered high strength due to metal concentrations and acidity orders of magnitude greater than typical amd discharges from both operating and abandoned portals as well as tailings related deposits displayed a high degree of heterogeneity with total metal concentrations ranging from 0 11 to 7480 0 022 to 889 0 0006 to 65 3 0 001 to 310 0 12 to 72 100 0 3 to 402 0 012 to 34 8 and 0 24 to 19 600 mg l of al as cd cu fe mn pb and zn respectively net acidity and ph ranged from 10 to 246 000 mg l as caco3 equivalent and 0 90 6 94 standard units respectively data were gathered during two sampling events centered around the most extreme periods of the dry and wet seasons of one water year loadings to local streams were marginally greater for most metals in the wet season if observed loadings are historically representative cerro rico amd has contributed thousands of tonnes of ecotoxic metals to the upper rio pilcomayo over the last five centuries metal and hydrogen ion concentrations in the majority of amd sampled were several orders of magnitude above discharge limits set by the bolivian government yet no action has historically or contemporarily been taken

contribution of mantle plumes crustal thickening and greenstone blanketing to the 2 75 2 65ga global crisis abstract assuming that the period 2 75 2 65 ga corresponds to a single but global geodynamic event we investigate through numerical experiments the mechanisms that could have led to the profound continental reworking that occurred at that time although the extent of the crisis at the earth s surface pledges in favour of the involvement of mantle plumes our numerical experiments suggest that the thermal impact of mantle plumes is unlikely to explain both the amplitude and timing of the thermal anomaly as observed in the superior province canada and the yilgarn craton australia similarly moderate crustal thickening can not lead to significant reworking of the continental crust within the observed time constraint crustal thickening with a factor 1 5 is also unlikely because it is not consistent with the moderate metamorphic grade observed at the surface of many archaean cratons burial of a radiogenic crust under a 10 km thick greenstone cover also falls short of explaining not so much the amplitude and the extent but the timing of the thermal anomaly in contrast the combination of the thermal anomaly related to the greenstone blanketing effect with the heat transfer from a plume head spreading at the top of the thermal boundary layer can adequately explain the amplitude the timing and the extent of the 2 75 2 65 ga crisis our favoured model involves a global rearrangement of convection cells in the deep mantle and formation of multiple mantle plumes the greenstones emplaced at the surface and the plumes that spread in the thermal boundary layer contributed to heat the crust from both above and below this produced massive crustal partial melting that reached its climax ca 40 myr after the emplacement of the plumes and associated greenstone cover rocks this led to gravitational instabilities in the crust as dense greenstone cover rocks began to sink into the thermally softened crust and granite domes rose in response the extraction of heat producing elements toward the upper part of the crust has contributed to the cooling and stabilisation of the cratons this succession of events which is not incompatible with plate tectonic processes may have profoundly changed the nature of the crust exposed at the surface and could explain the contrasting geochemical signatures of archaean and post archaean shales

the kapuskasing uplift a geological and geophysical synthesis over the past decade the kapuskasing uplift has been the subject of intense geological and geophysical investigation as lithoprobe s window on the deep crustal structure of the archean superior province enigmatic since its recognition as a positive gravity anomaly in 1950 the structure has been variably interpreted as a suture rift transcurrent shear zone or intracratonic thrust diverse studies including geochronology geothermobarometry and various geophysical probes provide a comprehensive three dimensional image of archean 2 75 2 50 ga crustal evolution and proterozoic 2 5 1 1 ga cooling and uplift the data favour an interpretation of the structure as an intracratonic uplift related to hudsonian collision eastward across the southern kapuskasing uplift erosion levels increase from 10 km in the michipicoten greenstone belt through the wawa gneiss domain 10 20 km into granulites 20 30 km of the kapuskasing structural zone juxtaposed against the low grade swayze greenstone belt al

archean continental assembly in the southeastern superior province of canada between 1988 and 1993 seismic reflection and refraction surveys were acquired across the medium to high grade opatica plutonic gneiss belt the low grade abitibi greenstone belt and the pontiac metasedimentary belt all of which form part of the late archean superior province shallowly north dipping reflections define a structural style consistent with the northward underthrusting and accretion over about 30 ma of various exotic terranes against a backstop provided by the opatica belt this rapid southward growth of the archean protocraton was driven by at least one north dipping subduction zone as revealed by north dipping reflections that extend to 65 km depth in the upper mantle below the opatica belt in contrast to the mainly orthogneissic opatica and pontiac belts the midcrust of the abitibi belt comprises metasedimentary and igneous rocks plus imbricated units of unknown affinity relict midcrustal accretionary complexes of substantial size whieh are indicative of primary suture zones are interpreted near the northern and southern limits of the abitibi belt an interpreted basal decollement and significantly older ages in the north suggest that the upper crustal greenstone rocks are allochthonous evidence of large scale extension appears to be confined to the southern volcanic zone of the abitibi which developed into a half graben as the original suture zone was reactivated in extension unusually high seismic p wave velocities 7 5 8 2 kms 1 are present in the lower 8 km of the abitibi crust and they correlate well with a downward reduction in seismic reflectivity attributable to late modification of the deepest part of the crust crustal xenolith studies suggest that this process may be linked to early proterozoic magmatism

intracrustal extension of an archean orogen revealed using single grain u pb zircon geochronology the metaplutonic wawa gneiss domain in the southern superior province is part of an uplifted block that was exhumed during the proterozoic exposing the lower crustal 30 km levels of the late archean 2720 to 2670 ma abitibi wawa orogen previous structural and geophysical studies of the midcrustal wawa gneiss domain reveal subhorizontal shear zones that formed during orogen parallel extension and correspond to gently dipping seismic reflectors present at depth elsewhere in the orogen in order to bracket the age of this extensional deformation the ages of metre scale igneous bodies that crystallized before and after extension have been determined in four outcrops using single grain u pb zircon dating techniques the results constrain the time of extension to the interval between 2660 and 2645 ma and show that deformation was coeval with pegmatite emplacement partial melting of tonalite gneisses as old as 2925 35 ma and regional circa 2660 ma granulite facies metamorphism of adjacent more deeply eroded crust this extension and associated high grade metamorphism in the wawa gneiss domain occurred 10 to 25 m y after the cessation of regional compression major transcurrent fault movement and sediment deposition in the upper structural levels of the orogen the middle and lower crust was therefore mechanically decoupled from the upper crust during this period of orogen parallel extension this intracrustal style of deformation is interpreted to be the consequence of gravitational forces working on a thermally softened middle crust the detachment of lithosphere from the orogen base is the favored mechanism for generating these forces and for introducing the heat that caused synextension metamorphism cyclic construction and delamination of orogen lithosphere could account for even younger metamorphic strain events evident in nearby exposures of lower crust

a detrital heavy mineral viewpoint on sediment provenance and tropical weathering in se asia abstract understanding heavy mineral preservation is important for interpreting generation pathways provenance and geochemistry of sediments despite this many assumptions about heavy mineral stability are based on ancient strata and few studies consider modern sediments particularly those in tectonically active tropical areas such as se asia we report new heavy mineral data on 69 river sand samples from the malay peninsula and sumatra in which one aim was to find provenance indicators specific to these areas identifications were performed using optical microscopy and confirmed with sem eds in the malay peninsula heavy minerals record granitic and contact metamorphic provenance variable amounts of zircon tourmaline hornblende andalusite epidote monazite rutile and titanite and minor amounts of pyroxene apatite anatase garnet diaspore colourless spinel cassiterite and allanite are typical of this source area the composition of assemblages from sumatra indicates contributions from two major sources the modern volcanic arc i and the basement ii abundant pyroxene particularly hypersthene up to 70 is diagnostic of the volcanic arc source vesuvianite garnet andalusite tourmaline chrome spinel rutile anatase and corundum are present only in small amounts

accretion of archean oceanic plateau fragments in the abitibi greenstone belt canada the arc arc collision model is often applied to the evolution of archean greenstone belts this model predicts concordant stratigraphic relations among the various lithologies evolving generally from komatiitic tholeiitic affinities toward calc alkalic affinities new geological data from the malartic composite block of the abitibi greenstone belt indicate that this volcanic pile rather than representing a conformable sequence is composed of four distinct mafic lithotectonic domains that are overlain by a calc alkalic sequence the mafic domains are thought to be examples of accreted archean oceanic plateau material that were deformed during their collage state the younger calc alkalic sequence represents extension related volcanism that erupted through the ac creted and deformed plateau material possibly as a consequence of ridge subduction in a regime of oblique convergence the relations described here may represent a common feature of archean terranes

sm nd lu hf and pb pb signatures of gneisses and granitoids from the la grande belt extent of late archean crustal recycling in the northeastern superior province canada abstract sm nd lu hf and pb pb isotopic signatures were determined for gneisses and felsic plutons of the la grande granite greenstone and the nemiscau metasedimentary belts of canada the northern part of the la grande belt exposes gneisses of the langelier complex formed between ca 2 8 and 2 9 ga the gneisses yielded end t values between 2 and 1 ehf t between 1 and 3 initial 207pb 204pb ratios of 14 9 higher than the value of 14 6 derived from the stacey kramers growth curve and crustal extraction ages 3 0 ga modeling shows that the syn to late tectonic intrusions of granitoid rocks record at least 20 and up to 40 recycling of this gneissic basement the southern part of the la grande belt where no basement gneisses are exposed records lower proportions 5 20 of this crustal end member in both parts of the la grande belt the post tectonic plutons record the largest proportion of recycled crust likely related to southeastward thrusting events in the superior craton crustal thickening and concomitant partial melting the la grande plutons have isotopic signatures more radiogenic than those of similar intrusions that formed concurrently to the south in the abitibi greenstone belt this reflects an ancient crust environment for the former vs an oceanic setting for the latter mantle reservoirs with a protracted history of incompatible element depletion were present beneath the whole eastern superior province in the late archean

characterization of acid mine drainage sources in the iberian pyrite belt base methodology for quantifying affected areas and for environmental management the present work aims to propose a methodology for quantifying the sources of acid mine drainage amd and to characterize the magnitude of the affected areas in the iberian pyrite belt sw spain such an approach allows the creation of a support tool for managing land and natural resources valorization which may be easily applied in similar mining regions the motivation and usefulness of this work can be realized by focusing on two main emerging strategic issues 1 water resources management with the example of alcolea dam that will receive water from affected areas in the iberian pyrite belt and 2 mineral resources valorization especially regarding copper exploration due to increasing market prices the used methodology included the following general steps it started with an inventory of the mines in the iberian pyrite belt followed by field cartography campaigns and finally the quantification of affected areas and contaminant discharges the results of the present work serve to confirm and quantify the magnitude of the amd pollution in the pyrite belt a total affected area of about 4 847 ha was estimated taking into account this figure and combining it with the annual average precipitation 650 l m2 results in an estimation of 31 503 680 m3 year of discharging water affected by the presence of sulphides in this scenario a total annual contribution of 260 056 tonnes year was obtained for sulphates which means more than 712 tonnes a day in the case of arsenic a toxic element the total annual contribution is more than 20 tonnes or close to 55 kg day regarding copper this economically interesting metal translates into total contributions of 10 364 tonnes year in the generating medium this gave more than 28 tonnes day which today sits at 8 200 dollars tonne this result suggests that solutions aimed at recovering this resource should be searched it may represent a financial return at the same time that it would mean overcome environmental liabilities

teleseismic studies of the lithosphere below the abitibi grenville lithoprobe transect in the past decade the abitibi grenville lithoprobe transect has been the site of numerous geological and geophysical surveys oriented towards understanding the lithospheric evolution of the southeastern superior and adjoin ing grenville provinces among the different geophysical methods that have been employed earthquake seismology provides the widest range of information on the deep structures of the upper mantle this paper presents a review of studies both complete and ongoing involving teleseismic datasets that were collected in 1994 and 1996 along the transect a complete shear wave splitting analysis has been performed on the 1994 dataset as part of a comparative study on electrical and seismic anisotropies results suggest a correlation between the two anisotropies supported by xenolith data and favour a lithospheric origin for the seismic anisotropy the two anisotropies are believed to represent the fossilized remnants of archean strain fields in the lithospheric roots of the canadian shield preliminary splitting results for the 1996 experiment suggest that the s wave azimuthal anisotropy may be depth dependent and laterally varying ongoing receiver function analysis and traveltime inversion studies provide velocity models of the crust and upper mantle beneath the study area preliminary receiver function results reveal the presence of an s velocity increase at 90 100 km depth which appears to be laterally continuous over 200 km traveltime inversion models indicate the presence of an elongate low velocity anomaly beneath the southern portion of the 1996 array which strikes obliquely to major geological structures at the surface e g grenville front preliminary interpretation relates this anomaly to the same process e g fixed mantle plume continental rifting responsible for the emplacement of the monteregian hills igneous province

geochemical study of different aged mining dump materials in the freiberg mining district germany historical mining dumps are useful archives for the investigation of weathering processes the objective of this study was to investigate the weathering behavior of waste rock material derived from the 800 year old silver ore mining in freiberg germany for identifying time dependent weathering indices dumped material of four dumps of different ages and corresponding rock was examined regarding the geochemical composition the dumped material is characterized by high contents of heavy metal containing sulfidic ores such as pyrite arsenopyrite sphalerite and galena acid mine drainage is produced by the oxidative weathering of the sulfide minerals and causes the increased dissolving of soluble metals with increasing age of dumps as a result of these weathering processes a clear depletion of chalcophile elements in the older dump material 800 years compared to the youngest dump 100 years was observed in the soil horizons downstream the dumps high quantities of heavy metals e g up to 12 000 ppm as 3 300 ppm pb 640 ppm zn mainly adsorbed on organic matter were determined and indicate a time dependent element transfer from the dumps into their surrounding soils

lode gold deposits and archean mantle plume island arc interaction abitibi subprovince canada abstract in combination with seismic interpretations and geochronological constraints the association of juvenile arc type low ti tholeiitic basalts with komatiites in the southeastern abitibi subprovince canada supports a history of subduction step back following late archean mantle plume island arc interaction the resulting paired collision zones preserved abundant komatiites and numerous massive sulphide deposits and established the critical metallogenic features to concentrate the majority of canada s precambrian gold resources in a small area of the southern abitibi subprovince

from gullies to mountain belts a review of sediment budgets at various scales this paper reviews the state of the art in the concept as well as in the application of sediment budgets in sedimentary research sediments are a product of mass dispersal at the earth surface and take part in global cycles sediment budgets aim at quantifying this mass transfer based on the principle of mass conservation and are the key to determine ancient fluxes of solid matter at the earth surface this involves fundamental questions about the interplay of uplift climate and denudation in mountain belts and transfer of sediments from the continents to the oceans as well as applied issues such as soil and gully erosion reservoir siltation and coastal protection first after introducing basic concepts relevant scales and methodologies the different components of quaternary routing systems from erosion in headwaters river systems glacial and paraglacial systems lakes deltas estuaries coasts shelves epicontinental seas and deep sea fans are discussed in terms of their sediment budget most suitable are sedimentologically closed or semi closed depositional environments e g alluvial fans lakes deltas and deep sea fans in a second step the dynamics of passive active and collisional tectonic settings and sediment budgets in related sedimentary basins are explored and new concepts of sediment portioning at large geodynamic scales are introduced ancient routing systems are more or less incomplete and may be intensively fragmented or destroyed in active tectonic settings in terms of sedimentary basin types rifts intracontinental and epicontinental settings are preferred objects of sediment budgets because of their persistence and relatively simple overall sedimentary architecture however closing basins such as foreland forearc retroarc piggy back and wedge top basins may provide excellent snapshots of orogenic sediment fluxes in a third step the large long lived routing systems of the amazon the ganges brahmaputra and the rhine are reviewed for each system estimates of either sediment volumes mass or sediment fluxes of continental and marine subsystems have been compiled in order to receive a complete routing in terms of mass conservation for specific time periods since the late glacial maximum as well as the cenozoic following lessons can be taken from these case studies i depositional centers and fluxes show strong shifts in space and time and call for caution when simply looking at subsystems ii the response times of these large systems are within the milankovich time interval thus lower than predicted from diffusion models iii cyclic routing of sediments in continental basins is much more dominated by climate human control than by eustacy and iv at long time scales ultimate sinks win over intermittent storage it is concluded from this review that the quantitative understanding of global sediment cycling over historic and geologic time and its response to allogenic forcing is still in its infancy and further research is needed towards a holistic view of sediment routing systems at various temporal and spatial scales and their coupling with global biogeochemical cycles this includes i to better determine response times of large routing systems by linking quaternary with cenozoic sediment budgets and continental with marine sub systems ii to combine advanced provenance techniques with sediment budgets in order to reconstruct ancient systems iii to study sediment partitioning at the basin scale iv to reconcile continental supply dominated sequence stratigraphy with the eustatic dominated marine concept and iv to account for non actualism of ancient systems with respect to their erosion and transport mode in particular during glaciations and pronounced arid intervals glacial and eolian sediment routing may cross over hydrologic boundaries of drainage basins thus challenging the principle of mass conservation

tectonic setting and terrane accretion of the archean zimbabwe craton the archean zimbabwe craton is made of a number of distinct tectonostratigraphic terranes assembled by plate tectonic processes the central tokwe terrane consists of 3 5 2 95 ga gneissic rocks and structurally complex inliers of possibly older greenstone belts these are overlain unconformably by a 2 9 2 8 ga assemblage of mafic and felsic volcanic rocks and conglomerates and a separate 3 0 2 7 ga southeastward thickening platform sequence of sandstone shale and limestone 2 7 ga greenstone belts form two distinctly different domains flanking the central terrane northwest of the ancient gneissic terrane ca 2 7 ga greenstone belts comprise a series of calc alkaline lavas and intercalated sedimentary rocks intruded by syn volcanic plutons southeast of the ancient gneissic complex 2 7 ga greenstone belts consist of thick piles of tholeiitic basalts overlying ultramafic lavas resting allochthonously over the shallow water platform sequence and older gneissic terrane this division of the zimbabwe craton is interpreted to show that the central tokwe terrane had a continental magmatic arc built on its northwestern edge as its southeastern margin rifted from another fragment forming the sea of umtali a passive margin sedimentary wedge formed on the rifted southeastern edge of this ancient continent and prograded onto the craton during sedimentary and tectonic loading of the craton margin the southeastern greenstone belts formed as thick oceanic crust oceanic plateau in this back arc basin and were later obducted on to the rift and passive margin sequence as the sea of umtali closed ca 2 7 ga this was followed by intrusion of granitic plutons of the chilimanzi suite ca 2 6 ga in a tectonic regime of intracontinental strike slip faulting representing a response to the zimbabwe kaapvaal continent continent collision crustal and lithospheric thickening during intrusion of these late granites may have played a role in stabilizing the zimbabwe craton and forming the lithospheric root

archean terrane docking upper crust collision tectonics abitibi greenstone belt quebec canada abstract the northern nvz and southern volcanic zones svz of the abitibi greenstone belt are separated by the major e trending destor porcupine manneville fault zone dpmfz the dpmfz is interpreted to be the locus of archean terrane docking between the older diffuse volcanic arc of the nvz 2730 2710 ma and the younger arc segments of the svz 2705 2698 ma two distinct evolutionary phases can be documented along the dpmfz of the abitibi greenstone belt and include 1 arc arc collision occurring between 2697 and 2690 ma and 2 arc fragmentation between 2689 and 2680 ma identification of these two events along the dpmfz is based on detailed structural studies sedimentary basin analysis and precise u pb age determinations the thrusting event representative of the arc arc collision phase is characterized by shallow north dipping foliations 20 40 and dip parallel stretching lineations in the eastern manneville segment of the dpmfz local overturned mafic pillowed units suggest recumbent folding late strike slip or transcurrent movement displayed in the late orogenic sedimentary duparquet basin records the arc fragmentation phase basin geometry e trending en echelon folds shallow e plunging stretching lineations and a late ne striking cleavage cross cutting the folds support a dextral shear sense along the western destor porcupine segment of the dpmfz the sedimentary facies observed in the basin are consistent with those of modern strike slip basins located along the east anatolian fault turkey hazar lake and the hope fault new zealand hanmer basin precise u pb zircon age determinations from porphyry stocks located at the northern and southern limits of the duparquet basin yielded 2681 1 ma and 2689 3 2 2 9 ma respectively these ages constrain the rapid change from thrusting to transcurrent movement it is apparent that once thrusting ceased the response to oblique subduction continued in the form of strike slip displacement modern fold and thrust belts commonly show this evolution the deformation pattern is the result of oblique convergence the abitibi greenstone belt is considered to be an archean analogue of modern subducting oceanic plates such as those found in the western pacific

komatiite flooding of a rifted archean rhyolitic arc complex geochemical signature and tectonic significance of the stoughton roquemaure group abitibi greenstone belt canada the 0 2 2 km thick archean stoughton roquemaure group srg in the northern volcanic zone of the abitibi greenstone belt quebec canada is composed of tholeiitic basalt komatiitic basalt and komatiite the mafic and ultramafic rocks are pillowed brecciated and massive columnar jointed flows the srg conformably overlies the 2730 ma hunter mine group a volcanic complex dominated by calc alkaline felsic rocks the tholeiitic basalts of the srg resemble morb the komatiitic basalts and komatiites have positive nd values overlapping those of the tholeiitic basalts komatiitic basalts with low al2o3 tio2 ratios 10 and fractionated heavy ree patterns are similar to al depleted komatiites in contrast the komatiites have high al2o3 tio2 20 unfractionated heavy ree patterns and resemble al undepleted munro type komatiites the al depleted komatiitic basalts occur at the base of the srg whereas the al undepleted komatiites are prevalent higher up in the stratigraphy the association of calcalka

role of lichens in weathering of granodiorite in the sila uplands calabria southern italy this paper explores the role of five recurrent epilithic lichen species aspicilia intermutans nyl arnold xanthoparmelia pulla ach o blanco a crespo elix d hawksw lumbsch rhizocarpon lecanorinum anders tephromela atra huds hafellner and lecanora bolcana pollini poelt which encrust granodiorite spheroidal boulders exposed in the sila uplands calabria southern italy in weathering of plutonic rocks in a typical mountainous mediterranean environment a detailed investigation was carried out on the lichen rock interface of each species by comparing them mutually and with lichen free granodiorite samples for this purpose the lichen species were sampled together with the encrusted rock surface for detailed mineral petrographic analyses performed in thin and ultra thin sections optical and scanning electron microscopy of these sections and of bulk samples permitted us to highlight the peculiar modes of physical and chemical attacks of lichen thalli and hyphae on and into the substratum for each species crack systems often parallel to the outer rock surface appear often intruded by hyphae which cause rupture of primary minerals with detachment and progressive incorporation of their fragments into the thallus in particular the species l bolcana and t atra revealed an unexpected partly endolithic behavior presumably enhanced by the presence of rock fractures earlier generated by other physical breakage processes already affecting the spheroidal boulders in the sila mountains dissolution features often affect primary minerals even quartz that may show very peculiar patterns which are suggestive of a biologically induced control various phyllosilicate clay minerals were identified using sem eds microprobe analyses and ft ir spectroscopy which also enabled the identification of possible amorphous silica or quartz micrograins rhizocarpic acid and carotenoid at the encrusted granodiorite interface in contrast neither oxalic acids nor oxalates were detected

a reply to how many arcs can dance on the head of a plume by jean bedard precambrian research 2012 abstract bedard s 2013 comment on wyman 2013 itself an outgrowth of a 5ias workshop debate has clarified several points concerning the catalytic delamination driven model of bedard 2006 many of the references to archean plate tectonic models however are expressed in terms of an improbable uniformitarian viewpoint that could not be applied to the modern earth whereas differences between archean and phanerozoic plateau basalts have been attributed to a less depleted mantle source any similar arguments from advocates of archean plate tectonics are characterized as special pleading bedard 2013 does not address key issues raised by wyman 2013 and when the paper does attempt to resolve apparent dilemmas related to craton development it undermines the new refinements made to the non plate tectonic scenario that bedard favors

plume and arc magmatism in the abitibi subprovince implications for the origin of archean continental lithospheric mantle abstract based on eclogitic mantle xenoliths that appear to be the residue of slab melts it is commonly argued that the formation of distinctive lithospheric keels beneath archean cratons occurred by the tectonic accretion of oceanic crust these models are complicated by evident buoyancy of the keels the varied compositions of the mantle xenolith suite as a whole and a compositional constraint that a large portion of the keels originated in mantle plume melting events resolution of these issues is complicated by the long development history of most cratons 100 s of m y and the multiple cycles of magmatism they represent in contrast the single 50 m y period of arc volcanism in the abitibi subprovince and the immediate onset of orogeny and craton stabilisation avoids many of these uncertainties chemical and isotopic data demonstrate that syn volcanic to syn tectonic adakitic abitibi granitoids were derived via slab melting deep seismic reflection profiles image singular slab like features along the moho these are interpreted as the remnants of oceanic slabs emplaced and torn during orogeny nonetheless their presence directly contradicts subcretion models of keel formation because they occupy regions that should correspond to the top of an earlier formed subcreted keel post adakite shoshonitic granitoids and lamprophyres also attest to the presence of a metasomatised mantle wedge throughout the entire period of abitibi arc magmatism diamond bearing lamprophyres in the abitibi and adjacent wawa subprovince are compositionally equivalent to paleoproterozoic diamondiferous rocks and characteristic of adakite generating shallow subduction rather than evidence of pre existing sub cratonic keels abitibi mantle plume and subduction related volcanism also demonstrates the continuous presence of shallow asthenospheric mantle beneath the belt over a 50 m y period komatiites and then boninites erupted along the central part of the belt halfway through its evolution and rifted arc style volcanism dominated the belt within a few m y of orogeny none of these events are consistent with the development of a progressively thickened continental lithospheric keel the geodynamic evolution of the abitibi belt demonstrates a fact recognised in some xenolith studies the characteristic association of deep keels and archean cratons was not developed gradually during greenstone belt volcanism rather it was initiated by the coupling of shallow imbricated plume and arc related crust with the buoyant residue of mantle plume melting that rose from depths of 80 km to 400 km subduction was active along the southern and eastern margin of the superior province craton before and after ascent of the abitibi plume renewal of subduction in the abitibi as marked by the occurrence of the 2716 ma boninitic volcanic suite delayed the ascent of the deep keel and its coupling to the composite crust final ascent of the plume residue occurred following orogeny and slab loss and may have included entrainment of fragmented slab residue into the rising diapir the coupling of shallow crust and deep keel occurred soon after and the keel s presence beneath the subprovince is recognised by phanerozoic diamond deposits xenolith chemistry and geophysical data

archean calc alkaline lamprophyres of wawa ontario canada unconventional diamondiferous volcaniclastic rocks abstract unusual diamondiferous rocks are found in the wawa subprovince of the southern superior craton they are dated at 2 67 2 7 ga and comprise part of a calc alkaline volcanic sequence of the michipicoten greenstone belt detailed mapping of an 40 km2 area showed that the rocks are metamorphosed polymict volcaniclastic breccia pvb and lamprophyre the breccia occurs as thick 60 110 m conformable beds traceable in intermittent outcrops along strike for more than 4 km whereas younger lamprophyre occurs as 0 5 3 m dykes magmatic predecessors for the metavolcanic rocks were determined on the basis of detailed mineralogical and petrographic observations and are found to be calc alkaline lamprophyres the only preserved magmatic phenocryst phase is coarse oscillatory zoned amphibole of edenitic and pargasitic compositions the parent magmas are similar in bulk composition to that of abitibi lamprophyres and other archean calc alkaline lamprophyres and may have thus also contained phenocrystal clinopyroxene and phlogopite the wawa lamprophyric magmas formed contemporaneously with felsic to mafic volcanic rocks and late orogenic intrusives of cycle 3 of the michipicoten greenstone belt they were emplaced episodically in local extensional areas in an active archean subduction zone the breccia formed as a volcaniclastic deposit and contains fragments of pyroclastic lapilli and juvenile material stratigraphy a wide range in clast lithologies poor sorting and paucity of sedimentary structures suggests the breccia formed in a debris flow the wawa diamondiferous rocks may be ancient equivalents of modern lamprophyric cinder cones and demonstrably associated epiclastic deposits

a comparative mineralogical and geochemical study of sulfide mine tailings at two sites in new mexico usa a comparative study of sulfide mine tailings from two sites near silver city in southwest new mexico has shown the need for environmental monitoring in a geological context the cyprus pinos altos and cleveland deposits consist of cu and zn skarn mineralization in the pinos altos mountains of new mexico primary ore minerals in both deposits include chalcopyrite sphalerite and galena the cyprus pinos altos mine ceased operation in 1995 and the cleveland mill closed in 1950 the deposits have similar mineralogical characteristics however the tailings are different in terms of age degree of oxidation and method of disposal the cyprus pinos altos tailings cpat are stored in a lined bermed impoundment they are dominantly water saturated and exhibit no secondary phase formation the grains are not cemented and show no evidence of primary mineral dissolution the geochemical data show a predominantly primary signature the tailings pond water is neutral to slightly alkaline ph from 7 to 8 3 partly as a result of processing methods the cleveland mill tailings cmt were deposited in a valley at the headwaters of an ephemeral stream they are highly oxidized and differentially cemented they have undergone numerous wet dry cycles resulting in extensive oxidation secondary minerals predominate and consist mainly of jarosite goethite hematite and fe oxyhydroxides and oxyhydroxysulfates the ph of the stream draining the cmt is as high as 2 15 maximum metal contents in the stream immediately downstream from the tailings are 5305 ppm zn 454 ppm cu 1 16 ppm pb 17 5 ppm cd 1 4 ppm as and 0 01 ppm hg

mineralogical and geochemical spatial analyses of a waste rock dump at the libiola fe cu sulphide mine eastern liguria italy in this work we investigated a 3 ha sulphide bearing waste rock dump libiola mine italy using mineralogical geochemical and geostatistical analyses the dumped materials were highly heterogeneous in grain size and lithology and varied both laterally and vertically other than the host rock of the ore basalts and serpentinites the dumped materials contained high amounts of low grade chalcopyrite and pyrite rich mineralisations due to these characteristics and to the absence of minerals able to neutralise acidity this waste rock dump can be classified as an acid mine drainage amd producer the study confirms that amd is still active and in the best scenario can persist for up to 6 17 103 years the consequences of this process are of serious environmental concern as it involves strong acidification of the circulating waters the release of potentially toxic metals into the soil streams and rivers and the precipitation of huge quantities of secondary fe oxides and fe oxyhydroxides

a special issue devoted to abitibi ore deposits in a modern context preface the abitibi greenstone belt which is part of the larger abitibi subprovince in the superior province of the canadian shield e g card and ciesielski 1986 is the largest known archcan greenstonegranite terrane 300 km n s x 400 450 km mineral production and reserves are significant particularly in relation to volcanogenic massive sulfide deposits and structurally controlled archcan goldbearing quartz vein systems the term au quartz vein being used in the sense of lindgren 1933 e g the gold quartz veins of ontario p 662669 volcanogenie massive sulfide production and reserves to 1989 1990 total 424 million metric tons

the evolution of the southern abitibi greenstone belt in light of precise u pb geochronology this paper summarizes u pb zircon ages for the archean southern abitibi greenstone belt and integrates them together with zircon and baddeleyite data for three new samples into a general framework for the evolution of the region new ages are reported for the ghost range gabbroic complex 2713 super 7 sub 5 ma and for a pyroclastic volcanic rock of the gauthier group 2700 or 3 ma a previously determined age of 2701 super 3 sub 2 ma for the felsic volcanic skead group is confirmed by magmatic zircons from a second sample that also contains a xenocrystic component or 2720 ma indicating that the skead volcano was built on top of an older volcanic sequence the compiled ages show that the southern abitibi greenstone belt developed between 2750 and 2670 ma the earliest ages date remnants of volcanic complexes that occur at the periphery of the belt major preorogenic magmatism was confined mainly to the period 2720 to 2700 ma in general each episode was characterized by the essentially coeval formation of komatiitic tholeiitic and calc alkalic igneous rocks taking into consideration the known geologic geochemical and isotopic data this association is consistent with evolution in paired active are and back are systems older crust was absent from the region but it may have interacted with these arcs and rift systems farther to the west the extensional regime was followed by a period of compression that caused folding and thrusting emplacement of calc alkalic plutons and deposition of turbidites between 2700 and 2688 ma the magmatism became predominantly alkalic during the main timiskaming period between 2681 and 2676 ma this event was accompanied by the deposition of alluvial fluvial sequences and was followed by renewed compression that caused polyphase folding and thrusting probably between approximately 2676 and 2670 ma lamprophyre dikes were associated with these final stages of deformation postorogenic activity includes faulting and episodes of hydrothermal activity locally associated with gold mineralization ages in the range 2630 to 2580 ma for hydrothermal minerals e g titanite and rutile camflo suggest a correlation of these events with lower crustal magmatism and metamorphism as recorded for example in the adjacent kapuskasing zone

groundwater hydrochemistry and soil pollution in a catchment affected by an abandoned lead zinc mine functioning of a diffuse pollution source the importance of polluted alluvial soils as a potential diffuse source of heavy metals was investigated in a catchment of the matylda stream affected by an abandoned lead and zinc ore mine in upper silesia southern poland this was attempted by means of standard groundwater analyses performed together with measurements of cd pb zn fe and mn concentrations in soil and groundwater the matylda stream receiving mine water was converted in the 20th century into a straight channel directed in its middle reach over the valley bottom this changed the drainage direction of the matylda stream water during mining operations groundwater seepage combined with surface drainage by shallow ditches caused pollution of sandy soils exceeding over 100 mg kg of cd 24 of zn and 4 of pb at surface or subsurface soil horizons and reaching at least 60 cm in depth after mine closure in the 1970s the network of ditches appears to be a source of ca mg chlorides carbonates and nitrates as indicated by the more or less regular increase of these major ion concentrations in groundwater down ditches whereas the ditches are a sink rather than a source of zinc cadmium and lead in permanently dry reaches or transition zones in reaches with surface water flowing periodically the metal concentrations and distribution in soil and groundwater suggest the slow mobilization of heavy metals stored in the valley bottom and the minor importance of soil as a diffuse source for surface water pollution

mine waste dumps and heavy metal pollution in abandoned mining district of boccheggiano southern tuscany italy mining activity in the boccheggiano fontalcinaldo area southern tuscany dates back at least to the 16th century ad and lasted up to very recent times copper rich hydrothermal veins massive pyrite deposits and their gossans were exploited two mine waste dumps fontalcinaldo fontebona one flotation tailings impoundment gabellino and one roasting smelting waste dump merse ribudelli in the study area were selected to ascertain the environmental effects of such protracted mining activity primary waste mineralogy is mainly characterized by pyrite gypsum quartz carbonates chlorites and micas secondary oxidation mineralogy includes fe and cu sulfates and hydroxy sulfates cu carbonates fe and al oxyhydroxides and other phases neogenic cassiterite at fontalcinaldo probable calkinsite ce la 2 co3 3 4h2o at fontebona mine waste samples show extremely variable contents of toxic elements cu pb zn bi cd as with average values in the order of hundreds to thousands of parts per million except for bi and cd in some samples the abundance of proper minerals of these metals cannot account for the entire metal load conceivably either solid solution substitutions or adsorption processes contribute to the intake of released metals into newly formed minerals release and transport of pollutants was affected to variable degrees by acid neutralization processes the highest metal and acid concentrations occur close to the investigated wastes and rapidly decrease moving downstream some hundreds of meters or less with the partial exception for mn and fe other than dilution effects this phenomenon may be ascribed to metal adsorption and precipitation of solid phases

heavy metal pollution in the surrounding ore deposits and mining activity a case study from koyulhisar sivas turkey the oxidation of sulfide minerals generates acidic waters containing high levels of so4 and fe the study area has active pb zn cu mining it is thought that the surface subsurface underground sulfide minerals in the region generally contribute to the acidification of groundwater low ph values are also responsible for dissolved metals al fe mn so4 pb zn in the groundwater and river furthermore current mining wastes have affected concentrations of trace elements in the water high fe and mn concentrations are generally found in the spring which has acidic and low eh values while al fe and mn concentrations in the acidic waters show notable increases with the maximum values reaching 8 829 19 084 and 1 708 ppb respectively these values exceed the turkish drinking water standard of 200 200 and 50 ppb respectively

sulfate and strontium water source identification by o s and sr isotopes and their temporal changes 1997 2008 in the region of freiberg central eastern germany abstract various waters bulk atmospheric precipitation groundwater river water flowing mine water mine drainage galleries and flooding mine water were studied in the region of freiberg to achieve an improved understanding of sources and mixing processes in the hydrological cycle and to specify the main sources that determine the isotope composition of dissolved sulfate and strontium 18 o so 4 34 s so 4 and 87 sr 86 sr in river water the combined use of isotope and chemical data led to identification of three major sulfate sources i sulfate from groundwater ii sulfate from the oxidation of local ore sulfides that remained in unflooded und flooded parts after mine decommissioning and iii industrial sulfate released from abundant waste slag and tailing deposits left behind after a long mining and industrial history of the region the same three components groundwater pore water from oxidation of residual ores and industry source were identified by analyzing sr isotope ratios however the sr isotopes pointed out a fourth yet unrecognized source that contributed to water of the flooded mine section the data show that the isotope composition of water of the river freiberger mulde was mainly determined by uncontaminated groundwater diluted with atmospheric precipitation whereas the other two end members played only a minor role for this river water however for the river triebisch the isotope compositions of dissolved sulfate and strontium record a strong impact of end members ii and iii after recharging the flooding water into the river a twelve year monitoring 1997 2008 revealed a strong decrease of 18 o so 4 values of water from bulk atmospheric precipitation as of 2006 2008 7 compared to 1997 14 while 34 s so 4 values remained constant 5 this isotope shift was probably caused by a lower contribution of primary sulfates to atmospheric precipitation in recent years groundwater and river water freiberger mulde also showed decreasing 18 o so 4 values albeit to a lower degree by 4 5 a decrease of 18 o so 4 values was again found in flowing mine water by 5 6 mainly affected by end member i uncontaminated groundwater the flood event in august 2002 likely washed out large parts of older groundwater and thus enabled the relatively large oxygen isotope decrease 18 o so 4 of groundwater and river water within a few years the previously high input from the industrial source waste and slag deposits decreased from 1997 to 2002 in some drainage galleries and flooding water that discharge their water into local rivers this led to lower 18 o and 34 s values of dissolved sulfates in these waters accompanied by a concentration decrease of several elements cl na and mg however no further decrease of the impact of this source could be detected after the storm and flood event in august 2002

a critical assessment of neoarchean plume only geodynamics evidence from the superior province abstract criticisms of archean plate tectonic models rarely offer detailed descriptions of alternative paradigms the catalytic delamination driven model for the coupled genesis of archean crust and sub continental lithospheric mantle described by bedard 2006 is an exception in that a relatively comprehensive but essentially 2 d model is described although this novel model is frequently cited as an example of the diversity in geodynamic thought for the archean it is rarely assessed with reference to events in a specific craton such as the superior province or a particular greenstone belt such as the abitibi when this type of assessment is undertaken it becomes clear that the apparent simplicity of the model one of its supposed virtues constitutes a critical weakness although bedard 2006 developed the catalytic model to overcome the perceived melt productivity deficit of archean plate tectonic models the catalytic process at the heart of the model is likely to be inefficient and provides insignificant improvements to crustal generation rates associated with subduction and non catalytic plume tectonics the model implies a near global craton in the mesoarchean to neoarchean but fails to address that fate of this craton during and after crustal rigidification seismic reflectors observed beneath archean cratons are characterized as failed delamination features but their global abundance suggests that syn to post tectonic ttg suites could not have been generated as a result of crustal restite delamination the brief descriptions of suggested mechanisms for the generation of minor rock types such as sanukitoids mask the complexity inherent in the overall model when considered in terms of the evolution of the superior province as a whole it is evident that many of these suggestions are not only implausible they are inconsistent with the timing and distribution of geological criteria used to mark the onset of crustal rigidification

quantitative models of sediment generation and provenance state of the art and future developments abstract an overview of quantitative approaches to analysis and modelling of sediment generation and provenance is presented with an emphasis on major framework components as determined by means of petrographic techniques conceptual models of sediment provenance are shown to be consistent with two classes of numerical statistical models i e linear mixing models and compositional linear models these cannot be placed within a common mathematical framework because the former requires that sediment composition is expressed in terms of proportions whereas the latter requires that sediment composition is expressed in terms of log ratios of proportions additivity of proportions a fundamental assumption in linear mixing models cannot be readily expressed in log ratio terms linear mixing models may be used to describe compositional variability in terms of physical and conceptual un mixing models of physical un mixing are appropriate for describing compositional variation within transport invariant subpopulations of grains as a result of varying rates of supply of detritus from multiple sources conceptual un mixing governs the relations among chemical mineralogical and petrographic characteristics of sediments which represent different descriptive levels within a compositional hierarchy compositional linear process models may be used to describe compositional and or textural evolution resulting from selective modifications induced by sediment transport as well as chemical and mechanical weathering current approaches to modelling of surface processes treat the coupled evolution of source areas and sedimentary basins in terms of bulk mass transfer only and do not take into account compositional and textural sediment properties moving from the inverse modelling approach embodied in provenance research to process based forward models of sediment generation which provide detailed predictions of sediment properties meets with considerable albeit not insurmountable problems strategies for developing more advanced parameterizations of sediment properties and for simulating their evolution are proposed and expansion of current data acquisition protocols is discussed in the light of data requirements for such advanced sediment generation models inclusion of sediment generation modules in models of landscape evolution and basin filling will mark a significant step towards full fledged source to sink simulations of earth surface processes

the timmins porcupine gold camp ontario anatomy of an archean greenstone belt and ontogeny of gold mineralization new structural and geochronological data and interpretations from the timmins porcupine gold camp abitibi subprovince more precisely define the stratigraphy and the generation timing and effects of deformation tisdale basalts and porcupine volcaniclastic and turbiditic sedimentary rocks assemblage rocks exhibit three major foliations s2 s3 s4 plus a late constrictional fabric of which s3 and s4 are also present in younger timiskaming assemblage sedimentary rocks pre timiskaming folding has long been recognized in tisdale assemblage rocks but no foliation had previously been attributed to such an event d1 regional uplift and extension produced a low angle unconformity between the tisdale and porcupine assemblages with partial excision of upper tisdale stratigraphy and perhaps of the blake river assemblage d2 involved imbrication of a set of south over north thrust sheets rooted in the porcupine destor deformation zone d3 en echelon folds along the northern flank of the porcupine destor deformation zone are a result of left lateral strike slip along this zone the timiskaming basin lying along the curvilinear trace of the porcupine destor deformation zone formed as a d3 transtensional half graben and the dome fault formed its faulted margin s4 foliation formed during subsequent right lateral strike slip movement and folding of s3 foliation intense d5 constrictional strain deformed earlier lineations as the previously dilatational jog that hosts timiskaming assemblage rocks acted as a compressional jog during right lateral movement along the porcupine destor deformation zone these d2 to d5 phases represent an overall thrusting strike slip transpressional regime there were several phases of gold mineralization in the timmins porcupine gold camp clasts of ankerite veins occur in timiskaming assemblage conglomerate at the dome mine and d3 foliation and folds crosscut early ankerite veining and alteration and some quartz veining thus low grade mineralization and possibly the quartz fuchsite veins predate timiskaming sedimentation however the bulk of gold postdates timiskaming sedimentation quartz carbonate tourmaline gold veins hollinger mcintyre hoyle pond dome aunor delnite mines formed within timiskaming assemblage and tisdale assemblage rocks these gold deposits developed largely as oblique slip and extensional vein arrays formed during north south shortening and local strike slip faulting younger deposits pamour are associated with d4 dip slip faulting and were weakly deformed during late d4 thus the largest known archean lode gold camp formed throughout protracted orogenesis consisting of a broadly transpressional regime with unusually well developed early thrusting

georadiochemical evidence to weathering of mining residues of the mansfeld mining district germany mining heaps are used as archives for the investigation of weathering processes aim of this work was to investigate the different weathering behavior of heap materials derived from kupferschiefer mining with respect to environmental hazard for this purpose kupferschiefer and slag material of two heaps of different age were examined regarding to the radionuclide distribution and geochemical composition by measuring of the local dose rate performing digital autoradiography and gamma spectrometry the radiological load of the heaps and the heap materials was determined the geochemical characterization of the samples was performed by xrf icp oes and icp ms the results show a clear higher radionuclide load of the younger slag heap a depletion of chalcophile and lithophile elements in the older slag was determined apart from a homogeneous radionuclide distribution considerable radionuclide enrichments in fossil fragments could be proven the results reveal a different weathering behavior of slag material in comparison to the kupferschiefer depending on the chemical binding of the elements on organic and inorganic species natural organic matter as well as apatite in kupferschiefer act as retention barrier for some metals

introduction to the special issue actualistic models of sediment generation conceptual models in sedimentary petrology that relate verticaland lateral compositional signatures during the lling of sedimentarybasins to their internal and external control factors have beendeveloped in the 80 ies and 90 ies of the last century althoughre ned petrographic and geochemical analyses have focussed ondeciphering complex events in time and space such as tectonic evo lution of source terranes changes in sediment dispersal patterns orpalaeoclimate uctuations quantitativemodelsarestillintheirinfancy despite a long history of research one reason for this state of affairs isthe strong interdisciplinary nature of the subject matter another isthe lack of appropriate modelling tools capable of dealing with thecomplex nature of sediment properties the recent proliferation ofquantitative data acquisition techniques coupled with progress indata processing and modelling approaches has led to the emergenceof a new eld of study aimed at solving the fundamental problem ofreconstructing mass transfer from source areas to sedimentary basins the term sediment generation acts as a convenient umbrella for thecomplex web of processes acting between source and sink quantitative models of sediment generation aim at providing anassessment of the type amount and rateof supplyof detritalmaterialfrom identi able parent rock assemblages to a basin ll in order toful l this objective two key questions must be addressed i how much sediment is being delivered ii what are the compositional and textural characteristics of thesediment the rst question is intimately connected to sediment budget as sessments and their derivative with respect to time i e erosion ordenudation and sedimentation rates the second one refers to the

stacked uppermost mantle layers within the slave craton of nw canada as defined by anisotropic seismic discontinuities 1 a 20 station seismic array in nw canada recorded 336 teleseismic events with distribution in back azimuth and epicentral distance sufficient to characterize uppermost mantle discontinuities between depths typical of the mohorovicic and lehman discontinuities following wavefield decomposition groups of seismograms were source normalized through simultaneous deconvolution to estimate the near receiver impulse response and thus detect major discontinuities beneath each seismic station stations within the lac de gras kimberlite field display an unusually strong negative impulse on the radial component within the nw quadrant and two moderate impulses on the transverse component forward modeling of these impulses suggests a mantle layer dipping at 22 to the southeast with a mildly anisotropic 2 upper discontinuity at 120 135 km depth and another mildly anisotropic 2 discontinuity at about 170 km depth superimposed on these layers is another stronger anisotropic 4 layer between 110 and 180 km depths that dips to the west stations outside of the lac de gras field but within the southeastern slave craton display more numerous but weaker impulses the most prominent of these occurs at about 150 km depth on the transverse component and has opposite polarity to that observed farther north the prominent negative impulse observed on the radial component is interpreted to arise from structural preferred orientation in the form of a stockwork of wehrlite dykes beneath the lac de gras field interpretation of the other layers in the context of known surface geology as well as xenolith petrology and garnet geochemistry of diamondiferous kimberlites favors previous suggestions that they represent 4000 2900 ma depleted harzburgite and eclogite layers underthrust from the northwest at 2600 or 1880 ma the layer beneath the se slave craton has a similar but distinct tectonic history of nw verging underthrusting associated with the 2635 2615 ma defeat suite of plutonism taken together these interpretations indicate that the slave craton was assembled from at least four lithospheric blocks prior to its cratonization about 2580 ma each block is 90 120 km thick and all four blocks abut across a steep suture boundary beneath mackay lake in the central slave craton significant amounts of carbon and eclogites could have become incorporated into the central slave mantle within the diamond stability field during the proposed underthrusting of lithosphere to explain their relatively common occurrence in kimberlite eruptions within the slave craton

formation of archean continental lithospheric roots the role of mantle plumes deep lithospheric roots commonly extending to the diamond stability field are distinctive characteristics of archean cratons but their origin remains controversial the 2 7 ga abitibi greenstone belt initially developed in an intraoceanic setting and provides unique insights into the formation of archean continental lithospheric mantle data provided by seismic transects young u pb isotopic ages in the exposed deeper crust of the kapuskasing uplift and anomalous ar ar isotopic ages from lode gold deposits point to a late coupling of the diamondiferous abitibi lithospheric mantle to arc crust these constraints and a lack of archean crust forming events following ca 2650 ma indicate that the thick abitibi cratonic root formed by the diapiric ascent of buoyant residue from which mantle plume derived komatiitic liquids had been extracted although substantial variation may have existed in the development of archean cratonic roots worldwide the evidence from the abitibi belt indicates that all such roots were initiated with the coupling of plume melt residue to greenstone belt crust