a precise late neoproterozoic u pb zircon age for the syntectonic perelle quartz diorite guernsey channel islands uk a precise u pb zircon age of 611 4 2 0 1 1 ma has been determined for the foliated quartz diorite at perelle bay guernsey uk channel islands the age is based on the analysis of single zircons half of a single grain and groups of two and three zircons the age is nearly 100 ma younger than that suggested by other workers based on 207 pb 206 pb dates of large multi grain fractions of zircon and thus rules out this intrusion as the earliest marker of the onset of cadomian magmatism in the north armorican massif a 611 ma crystallization age for the perelle quartz diorite is consistent with previous detailed fabric development studies that suggested magmatic fabrics within the pluton are largely overprinted by similarly oriented solid state deformation fabrics resulting from syntectonic emplacement during cadomian orogenesis the u pb age is approximately 8 15 ma older than 40 ar 39 ar hornblende dates for the pluton consistent with the emplacement of the intrusion followed by slow cooling in a region of moderate to high ambient crustal temperatures these new data emphasize the fact that periods of pluton emplacement are considerably briefer than periods of deformation and thus syntectonic intrusions do not date regional deformational events but only mark events within a period of regional tectonism the ability to analyse single zircons and selected portions of single zircons using ultra low blank u pb analytical techniques documents the feasibility of determining precise emplacement ages of other neoproterozoic granitoids that contain a significant percentage of xenocrystic zircon

modeling of multicomponent reactive transport in groundwater 2 metal mobility in aquifers impacted by acidic mine tailings discharge the mobility of potentially toxic dissolved metals discharged from a mine tailings source into an aquifer is investigated by using the multicomponent reactive transport model mintran a generic aquifer resembling a site in northern ontario is used as a basis and a scenario analysis is performed to determine the effect of terminating the source input of acidity and dissolved metals after a finite time it is found that for most metals the buffering reactions in the carbonate aquifer lower the dissolved metal concentrations substantially often by several orders of magnitude in the case of a 12 year source duration most metals are effectively immobilized by precipitation and the concentrations of metals remaining in solution are well below drinking water limits the risk of contamination of water resources by toxic metals can thus be controlled

hydrochemical characterisation of water quality in the sarcheshmeh copper complex se iran hydrochemical investigations were conducted to identify variations in surface water chemistry in different parts of the sarcheshmeh copper complex twenty three water samples from mine drainage stream water processing water of the concentrator plant and tailings dam water were collected to understand processes that control the elements mobility changes in trace metal concentrations and variation of major ions show two distinct water types a neutral mine drainage nmd associated with the sarcheshmeh mine waters containing lower trace metal so42 concentrations and neutral ph values and b acid mine drainage amd with waters from tailings impoundments and waste rock dumps corresponding to higher trace metals fe cu zn mo and major anions so42 and cl than the first type with typically acidic ph contents as a result of cu mo sulphides flotation process under alkaline conditions high ph values high mo concentration and low contamination loads of al mn fe cu and cd were observed in reject waters from the concentrator plant sulphide oxidation especially pyrite dissolution precipitation of the secondary minerals and discharge of the reject waters from concentrator plant were some of the most important factors that influence water quality at the tailings impoundments the results of phreeqc speciation and solubility modelling indicated supersaturation of the waters in the tailings impoundments with respect to hydronium jarosite schwertmannite and gypsum

short paper cadomian terrane tectonics and magmatism in the armorican massif the north armorican composite terrane nw france is a collage of displaced terranes which result from the amalgamation of cadomian continental arcs and marginal basin complexes by sinistral transpression along a continental margin above a subduction zone early cadomian arc activity occurred at c 700 650 ma but terrane accretion did not occur until c 540 ma and post tectonic magmatism persisted well into the palaeozoic cadomian events thus span a considerably greater period than previously supposed

tectonothermal chronology of early cadomian arc development in guernsey and sark channel islands the cadomian orogen exposed in nw france and the channel islands comprises a collage of variably displaced terranes which record the late proterozoic evolution of a continental margin within a complex subduction zone on the islands of guernsey and sark calc alkaline quartz diorite stocks were emplaced during early stages of the cadomian orogeny zircons from two stocks of deformed quartz diorite display evidence of inheritance in larger and more magnetic fractions upper intercept ages for these discordant concentrates are c 1300 ma sm nd whole rock model ages t dm suggest older ages of c 2000 ma conversely the smallest and least magnetic zircons exhibit a distinct lead loss pattern suggesting that the 207 pb 206 pb dates of c 700 ma correspond to the time of crystallization of the stocks and provide a lower age constraint for initiation of subduction related magmatism in the cadomian orogen hornblende concentrates from deformed quartz diorite stocks exposed on guernsey and sark display discordant 40 ar 39 ar age spectra five samples record well defined isotope correlation ages ranging between 596 ma and 606 ma a hornblende concentrate from host orthogneiss sark yields a plateau age of 608 ma the hornblende ages are interpreted as dating post metamorphic cooling following late proterozoic deformation and metamorphism within the arc system both magmatic and cooling ages from this early cadomian arc contrast with those of younger initial tectonothermal activity c 570 ma and c 540 ma in other cadomian terrane elements and suggest palinspastic separation until very late stages of the orogeny the polyphase nature of this late proterozoic activity is similar to that of related orogens which probably occupied similar tectonic settings along the margin of gondwana e g sw iberia west africa

odm an analytical solution based tool for reacting oxygen diffusion modelling in mine spoils a simple one dimensional analytical solution is presented to model oxygen diffusion through the pore space of mine spoils containing pyrite the model incorporates volumetric oxygen consumption terms due to pyrite oxidation oxidation of fe 2 to fe 3 and bacterial activity based on this analytical solution a graphical user interface gui tool is programmed and designed in matlab software this tool can be used to model transport of oxygen through the mine spoils either with or without a cap results of several simulation scenarios of sensitivity analysis showed a significant change in oxygen concentration with varying effective diffusion coefficient of oxygen transport model and simulation time efficiency and flexibility of the tool developed here is verified by modelling oxygen transport through the pore space of a coal waste pile case a and a copper mine tailings case b maximum depth of oxygen diffusion is obtained approximately equal to 2 and 1 5 m through the cases a and b respectively

the role of pre existing precambrian structures in rift evolution the albertine and rhino grabens uganda abstract we integrated shuttle radar topography mission srtm digital elevation models dem airborne magnetic radiometric and three dimensional full tensor gravity gradiometry 3d ftg data to investigate the role of precambrian structures in the evolution of the largely amagmatic miocene recent aged albertine and rhino grabens in uganda these grabens represent the northern segment of the western branch of the east african rift system ears the two ne trending grabens are connected by a right stepping transfer zone and they extend within the archean paleoproterozoic northeast congo block which represents the northeastern extension of the congo craton our results show the following and highlight the importance of pre existing structures in the evolution of continental rift systems 1 the ne extent of the albertine full graben is controlled by ne trending precambrian fabric and the graben terminates at its northeastern end when it encounters a multiply folded precambrian basement terrain with poorly developed nw trending structural grain additionally the northeastern termination of the albertine graben coincides with the presence of nw trending right stepping high density bodies within the precambrian terrain 2 the transfer zone between the albertine and rhino grabens is controlled by ne trending precambrian structures which might have facilitated the development of relay ramp faults 3 strain localization within the better developed southeastern border fault of the rhino half graben is facilitated by the presence of precambrian structures better aligned in a ne direction in the southeastern part of the basin compared to its northwestern part 4 further to the northeast the rhino graben is segmented and transitions into a narrower ene trending half graben with a better developed border fault on its northwestern side this segmentation coincides with the presence of n trending precambrian structures 5 the rhino graben terminates farther northeast against the nw trending precambrian aswa shear zone a prominent structure with complex but generally nw trending fabric

deformation of granitic rocks across the brittle ductile transition abstract a microstructural analysis has been carried out on mylonites and mylonitic gneisses of the eastern peninsular ranges mylonite zone which were formed over a range of metamorphic conditions from lower greenschist to amphibolite facies composite planar fabrics in the form of c and s planes are found at all metamorphic grades fractured feldspars kinked biotites and ductile deformation of quartz characterize the lower greenschist facies mylonites at mid upper greenschist grade orthoclase grains show dynamic recrystallization textures whereas plagioclase exhibits low temperature plasticity with only minor recovery biotite ribbons form by progressive rotation and coalescence of kink band segments to produce chevron fold patterns at epidote amphibolite grade and above recovery processes and annealing recrystallization predominate in all minerals residual orthoclase porphyroclasts show strain related myrmekite formation along those sides of the grains that face the instantaneous shortening direction myrmekite formation due to replacement reactions cannot explain this geometry it is proposed that the myrmekites formed due to a combination of exsolution replacement and strain enhanced diffusion

release transport and attenuation of metals from an old tailings impoundment abstract the oxidation of sulfide minerals from mine wastes results in the release of oxidation products to groundwater and surface water the abandoned high sulfide camp tailings impoundment at sherridon manitoba wherein the tailings have undergone oxidation for more than 70 a was investigated by hydrogeological geochemical and mineralogical techniques mineralogical analysis indicates that the unoxidized tailings contain nearly equal proportions of pyrite and pyrrhotite which make up to 60 wt of the total tailings and which are accompanied by minor amounts of chalcopyrite and sphalerite and minute amounts of galena and arsenopyrite extensive oxidation in the upper 50 cm of the tailings has resulted in extremely high concentrations of dissolved so4 and metals and as in the tailings pore water ph 1 m thick geochemical modeling and mineralogical analysis indicate that the hardpan layer consists of secondary melanterite rozenite gypsum jarosite and goethite the minerals indicated mainly control the dissolved concentrations of so4 fe ca and k the highest concentrations of dissolved metals are observed directly above and within the massive hardpan layer near the water table at a depth of 4 m most metals and so4 sharply decline in concentration although dissolved concentrations of metals and so4 decrease below the water table these concentrations remain elevated throughout the tailings with up to 60 600 mg l 1 fe and 91 600 mg l 1 so4 observed in the deeper groundwater during precipitation events surface seeps develop along the flanks of the impoundment and discharge pore water with a geochemical composition that is similar to the composition of water directly above the hardpan these results suggest that shallow lateral flow of water from a transient perched water table is resulting in higher contaminant loadings than would be predicted if it were assumed that discharge is derived solely from the deeper primary water table the abundance of residual sulfide minerals the depletion of aluminosilicate minerals in the upper meter of the tailings and the presence of a significant mass of residual sulfide minerals in this zone after 70 a of oxidation suggest that sulfide oxidation will continue to release acid metals and so4 to the environment for decades to centuries

time span of plutonism fabric development and cooling in a neoproterozoic magmatic arc segment u pb age constraints from syn tectonic plutons sark channel islands uk abstract new u pb zircon and titanite dates from syn tectonic plutons on the british channel island of sark constrain the time span of plutonism fabric development and cooling in this part of the neoproterozoic cadomian magmatic arc the tintageu leucogneiss is a mylonitic unit that was dated previously at 615 6 4 2 2 3 ma the port du moulin quartz diorite which intruded the tintageu unit contains a high strain solid state deformation fabric that is less intense than but parallel to fabrics in the leucogneiss and yields a u pb zircon date of 613 5 2 3 1 5 ma the little sark quartz diorite also displays solid state deformation fabrics in addition to relict magmatic textures and yields a u pb zircon date of 611 4 2 1 1 3 ma the north sark granodiorite is largely penetratively undeformed exhibits mainly magmatic fabrics and textures and has a u pb zircon date of 608 7 1 1 1 0 ma two fractions of titanite from each intrusion are essentially concordant and are identical within error with mean dates of 606 5 0 4 ma port du moulin quartz diorite 606 2 0 6 ma little sark quartz diorite 606 4 0 6 ma north sark granodiorite the new u pb data in combination with previous u pb and 40 ar 39 ar data and previous field studies confirm the syn tectonic nature of the sark plutons and quantify the time span ca 7 m y required for intrusion and sufficient crystallization of each body to record incremental strain during waning deformation titanite u pb and hornblende 40 ar 39 ar dates mark final cooling about 2 m y after intrusion of the last pluton

significance of a hiatus in down temperature fabric development within syn tectonic quartz diorite complexes channel islands uk detailed fabric development histories have been deduced for neoproterozoic foliated quartz diorite complexes of the channel islands uk the plutons were emplaced during regional d2 deformation magmatic fabrics formed at low crystal contents pre rheologically critical melt percent are only locally preserved due to overprinting by solid state deformation which occurred at moderate temperatures 400 550 c this is demonstrated by brittle microcracking of plagioclase and amphibole with only local ductile bending and dynamic recrystallization marginal recrystallization and myrmekite development on alkali feldspar ductile deformation of quartz to form types 2 3 ribbons quartz recrystallization by sub grain rotation associated with a slip but not c slip biotite recrystallization within micro shears and variable amphibole recrystallization the deformation histories display a distinct division between magmatic state and moderate temperature solid state deformation features with little evidence for intervening high temperature solid state fabrics this contrasts with criteria widely considered diagnostic of syn tectonic plutons which envisage development of a continuum of magmatic through high temperature solid state deformation fabrics however we consider the plutons syn tectonic and attribute the hiatus to contrasting strain and pluton cooling rates length and nature of deformation events and host rock ambient temperatures intermediate magmas emplaced at moderate to shallow levels in the crust may be more prone to develop such apparently punctuated deformation histories than sio 2 richer granitoids

timing of post tectonic cadomian magmatism on guernsey channel islands evidence from 40ar 39ar mineral ages the channel island of guernsey exposes pre and post tectonic calc alkaline plutonic rocks attributed to late precambrian cadomian subduction activity 40 ar 39 ar mineral cooling ages presented here clarify the age and time span of post tectonic intrusions amphibole from the bon repos meladiorite yields an isotope correlation age of 605 3 4 6 ma indicating emplacement during late stages of the tectonothermal event recorded within its host rocks igneous hornblendes from the northern igneous complex record consistent isotope correlation ages st peter port gabbro 570 2 1 1 ma bordeaux diorite complex 569 0 1 1 and 565 3 2 2 ma and a comagmatic enclave within cobo granite 570 2 1 5 ma hornblende and biotite from contact metamorphosed host rocks adjacent to the cobo granite yield isotope correlation ages of 569 6 1 1 and 563 8 3 3 ma respectively these ages together with field data demonstrate that the various members of the northern igneous complex were emplaced contemporaneously at c 570 ma significantly earlier than a c 500 ma rb sr whole rock isochron age previously reported for the cobo granite the 40 ar 39 ar ages indicate that post tectonic magmatism on guernsey was broadly coeval with post metamorphic cooling around the baie de st brieuc on the adjacent french mainland and occurred c 30 ma prior to peak cadomian deformation and metamorphism in the st malo area

exsolution in hornblende and its consequences for 40ar39ar age spectra and closure temperature abstract step heating studies of hornblende and biotite which coexist in an amphibolite near north walpole vermont reveal dramatically different 40 ar 39 ar age spectra the biotite mg 59 is characterized by a plateau over 98 percent 39ar release at 343 5 ma in strong contrast to the amphibole which exhibits both a complex age spectrum and a k ar age significantly younger than the biotite the amphibole release pattern contains three complete age cycles which range between extremes of 199 ma and 408 ma interestingly the k ca ratio calculated from reactor produced isotopes also varies with ar release but follows a trend which is antipathetic to the 40 ar 39 ar age pattern detailed microstructural examination including transmission electron microscopy tem reveals a complex exsolution structure that is consistent with both the complexity of the release pattern as well as the low degree of radiogenic 40ar 40ar retentivity in the amphibole this result underscores the variability of closure temperature tc for 40ar in metamorphic amphiboles and should warn against accepting a single universal value of tc

neoproterozoic shear zone tectonics within the icartian basement of guernsey and sark channel islands the channel islands of guernsey and sark are amongst the few localities within the neoproterozoic cadomian orogenic belt where palaeoproterozoic basement is exposed basement units collectively referred to as icartian comprise orthogneisses e g the c 2000 ma icart granite gneiss metasediments and amphibolites on guernsey the protolith to the icart granite gneiss was intruded into metasediments already deformed during a d 1 deformation event both were variably deformed during a d 2 event within an approximately north south trending steeply dipping oblique dextral shear zone on sark metasediments and amphibolites carry a d 1 fabric not necessarily correlatable with that on guernsey which was deformed during d 2 to form recumbent gently inclined folds and tectonic fabrics which locally carry top to the south kinematic indicators early cadomian quartz diorites which intruded the icartian basement carry variably developed magmatic and moderate temperature 400 550 c ls solid state fabrics which are similarly oriented to d 2 basement structures this indicates that the quartz diorites were emplaced and deformed during a protracted d 2 event published 40 ar 39 ar amphibole cooling ages of c 600 ma from guernsey and sark quartz diorites and a host icartian amphibolite are consistent with reworking of basement units during the cadomian orogeny the contrasting kinematic pattern during cadomian deformation implies that a flat lying shear zone on sark may have accommodated oblique dextral strike slip movement on guernsey with an overall southerly direction of tectonic transport deformation most likely occurred in the hanging wall of a major south dipping neoproterozoic subduction zone

chronology of cadomian tectonothermal activity in the baie de saint brieuc north brittany france evidence from 40ar 39ar mineral ages the late precambrian cadomian orogen exposed in the north armorican massif northwest france is a collage of displaced terranes that in part developed during amalgamation of continental arc and marginal basin complexes 40ar 39ar mineral ages reported here place new constraints on the timing of cadomian tectonothermal activity in the southern part of the st brieuc terrane in the baie de saint brieuc area brioverian supracrustal units were deformed metamorphosed and intruded by calc alkaline plutonic complexes metamorphic hornblende from a metabasic amphibolite sheet within brioverian rocks records an isotope correlation age of 568 4 2 6 ma interpreted to date postmetamorphic cooling through appropriate argon closure temperatures similar isotope correlation cooling ages are recorded by metamorphic hornblende within both an amphibolite sheet intrusive into the penthievre complex 567 5 1 2 ma and the la croix gibat amphibolite 574 8 2 1 ma igneous hornblende from the late tectonic to pos

a new high precision u pb date from the oldest known rocks in southern britain a new high precision u pb zircon age of 710 8 1 5 ma for granophyric granitic rock from the stanner hanter complex of the welsh borderland lies just within error of an older rb sr isochron age nd values of 0 3 and 1 2 combined with t dm of 1394 ma and 1468 ma indicate that the magma incorporated an older crustal source component the nd data highlight differences with western avalonia the widely considered late neoproterozoic north american counterpart to southern britain and point toward a closer similarity with other peri gondwanan terranes that incorporate older cratonic source material

environmental geochemistry of rare earth elements in cu porphyry mine tailings in the semiarid climate conditions of sarcheshmeh mine in southeastern iran abstract sarcheshmeh mine is one of the largest oligo miocene porphyry cu deposits in the world it is located in the kerman cenozoic magmatic arc in southeastern iran this paper discusses the geo environmental behavior of rare earth elements rees in the sarcheshmeh dammed tailing pond situated in semiarid climate for this purpose solid and water samples were collected to consider 1 weathering oxidation reactions and upward migration of soluble elements 2 super saturation and formation dissolution of the secondary evaporative phases 3 hydro geochemical changes of the surface and groundwater resources 4 flotation of the cu sulfide ore and tailing management strategies the mean values of the rees for fresh and weathered tailings and the evaporative phases were 113 0 103 7 and 74 6 mg kg respectively when compared with the fresh and weathered tailings the evaporative phases showed significant enrichment of hrees and a well depleted pattern of lrees except for that of eu this geochemical pattern suggests a higher solubility and mobility potential of hrees and eu compared with lrees resulting in good fractionation and enrichment of these elements in the surface evaporative layer formed on top of the weathered tailings the water samples showed a range of hydro geochemical features under acidic ph of 2 5 to 4 7 near neutral ph of 6 4 to 7 9 alkaline ph of 8 to 10 and highly alkaline ph 10 conditions the maximum concentration of rees was observed in the acidic waters produced by the weathered tailings after rainfall rees of 489 to 1903 g l although rees decreased as the ph value increased the general trend was compatible with the highest concentration of hrees rather than lrees the speciation calculations indicate that lnso4 ln so4 2 and ln3 are the primary forms of dissolved rees at acidic and near neutral ph and the dominant species was lnso4 lnco3 40 78 ln co3 2 31 68 and lnso4 31 07 were the dominant species under alkaline conditions at high alkaline ph the speciation pattern changed to lnoh2 53 15 ln co3 2 44 88 and lnco3 2 61 where ln denotes lanthanide based on the results and considering previous works it appears that ionic potential plays an important role in the geo environmental behavior of rees of adsorption tendency mobility potential and ionic substitution

pollution of a water course impacted by acid mine drainage in the imgok creek of the gangreung coal field korea abstract the purposes of this study are to i determine the geochemical characteristics of imgok creek impacted by acid mine drainage amd generated from abandoned coal mines ii to assess the pollution of heavy metals in the stream sediments and soils and iii to identify the chemical form of fe precipitates collected in the study area where there are 4 abandoned coal mines which belong to the grangreung coal field at the eastern part of korea amd generated from mine adits and coal refuse piles shows low ph and high concentrations of fe al and so 4 especially in the youngdong coal mine in imgok creek ph values increased and total dissolved solids tds values decreased with distance the concentrations of toxic heavy metals and major cations except fe decreased by dilution but the concentration of fe decreased rapidly due to the formation of precipitates the quality of groundwater samples did not exceed the korean drinking water standard in the stream sediments the concentrations of fe are relatively high in the youngdong tributary and imgok creek but the concentrations of heavy metals are similar to those of unpolluted sediments pollution indices of agricultural soils range from 0 28 to 0 47 yellowish red fe precipitates collected in the study area turned out to be amorphous or poorly crystallized minerals determined by x ray diffraction patterns and fe ox fe tot ratios and to contain chemically bonded so 4 and oh determined by infra red ir spectral analysis with these the mol ratios of fe s ranging from 4 6 to 6 1 determined by electron probe micro analysis epma in precipitates strongly support the existence of schwertmannite

geochemical distribution and removal of as fe mn and al in a surface water system affected by acid mine drainage at a coalfield in southwestern china the chemical characteristics formation and natural attenuation of pollutants in the coal acid mine drainage amd at xingren coalfield southwest china are discussed in this paper based on the results of a geochemical investigation as well as geological and hydrogeological background information the chemical composition of the amd is controlled by the dissolution of sulfide minerals in the coal seam the initial composition of the groundwater and the water rock interaction the amd is characterized by high sulfate concentrations high levels of dissolved metals fe al mn etc and low ph values ca2 and so42 are the dominant cation and anion in the amd respectively while ca2 and hco3 are present at significant levels in background water and surface water after the drainage leaves the mine site the ph and alkalinity increase asymptotically with the distance along the flow path while concentrations of sulfate ferrous iron aluminum and manganese are typically controlled by the deposition of secondary minerals low concentrations of as and other pollutants in the surface waters of the xingren coalfield could be due to relatively low quantities being released from coal seams to adsorption and coprecipitation on secondary minerals in stream sediments and to dilution by unpolluted surface recharge although as is not the most serious water quality problem in the xingren region at present it is still a potential environmental problem

a review of criteria for the identification of magmatic and tectonic foliations in granitoids abstract foliations in granitoids can form by magmatic flow submagmatic flow high temperature solid state deformation and moderate to low temperature solid state deformation a review of previous work suggests that no single criterion can consistently distinguish foliations in granitoids formed by flow during ascent diapiric emplacement and expansion emplacement during regional deformation or regional deformation post dating emplacement however a magmatic origin is favoured for foliations defined by the alignment of igneous commonly euhedral minerals particularly where the foliation is parallel to internal or external pluton contacts foliations formed during expansion or ballooning of diapirs may be strictly magmatic in origin although some studies suggest that solid state deformation also may occur if so we would hope to find evidence of deformation of crystal melt systems and that the solid state deformation occurred at high temperatures the inference of syntectonic foliations is most convincing where magmatic and high temperature solid state foliations are subparallel these foliations are continuous with regionally developed foliations in the wall rocks synkinematic porphyroblasts are present in the wallrocks and igneous minerals have the same age as metamorphic minerals associated with the regional cleavage a strictly tectonic origin for foliations in granitoids is favoured when the foliation is defined by metamorphic minerals no alignment of igneous minerals occurs the foliation is locally at high angles to pluton wallrock contacts and the foliation is continuous with a regionally developed cleavage

characterisation of the sarcheshmeh copper mine tailings kerman province southeast of iran mineral processing operation at the sarcheshmeh porphyry copper mine has produced huge quantities of tailings materials containing sulphide minerals in particular pyrite these tailings materials were geochemically and mineralogically characterised to assess pyrite and chalcopyrite oxidation acid mine drainage generation and trace element mobility to lead development of a proper remediation plan five vertical trenches up to 4 2 m deep were excavated from the tailings surface and 70 solid samples were taken in 0 3 m intervals the samples were first mineralogically analysed pyrite was the main sulphide mineral found in the tailings the gangue minerals include quartz muscovite illite chlorite albite orthoclase halite the samples were geochemically analysed for total concentrations of 62 elements paste ph so4 2 co3 2 and hco3 the maximum concentrations of so4 2 1 300 1 170 1 852 1 960 and 837 mg l were observed at a depth of 0 9 m in profiles a b c d and e respectively the tailings have a high acid producing potential and low acid neutralising potential pyrite 4 6 wt calcite 1 wt fe2 so4 3 cuso4 mgso4 and mnso4 were the dominant secondary sulphate minerals in the tailings the lowest ph values 2 9 3 and 3 were measured at a depth of 0 3 m in the profiles a b and c 3 9 at a depth of 0 6 m in the profile d and 3 at a depth of 0 9 m in the profile e the upper portions of the profiles c 1 8 m and d 2 1 m were moderately oxidised while oxidation in the profiles a b and e did not extend more than 1 2 1 2 and 1 5 m beneath the tailings surface zn pb rb u hf nd zr and ga show almost a constant trend with depth cd sr th la and ce increased with increasing depth of the tailings materials while co v ti cr cu as mn ag mo and ni exhibit initially a decreasing trend from tailings surface to the depths that vary between 0 9 and 1 2 they then remained constant with the depth the results show pyrite and chalcopyrite oxidation at surface layers of the tailings and subsequent leaching of the oxidation products and trace elements by infiltrated atmospheric precipitation

timing of cadomian deformation and magmatism within la hague nw france the la hague peninsula normandy nw france contains the most northerly components of the late neoproterozoic cadomian orogeny u pb dates for single grain and small multiple grain zircon separates from carefully selected plutons provide geochronological constraints on the timing of deformation and magmatism within the region the syntectonic jardeheu quartz diorite and omonville granodiorite were emplaced and contemporaneously deformed during the development of a greenschist facies fabric pervasive across the peninsula u pb zircon dates of 610 1 ma for the jardeheu quartz diorite and 608 2 ma for the omonville granodiorite are similar to a previously reported sensitive high resolution ion microprobe u pb date for metamorphism of the basement and indicate that a regionally significant period of metamorphism and magmatism occurred between 620 and 608 ma an emplacement age of 573 9 1 3 0 9 ma for the syntectonic thiebot granodiorite places limits on the timing of deformation along the thiebot shear zone zircons from the undeformed st martin monzonite give a precise u pb age of 581 3 1 1 ma the new dates point to reactivation of magmatism and localized greenschist facies deformation between 582 and 573 ma

u pb geochronology and sm nd isotopic composition of proterozoic gneisses channel islands uk gneissic units of the channel islands united kingdom have traditionally been considered to be palaeoproterozoic basement to the late neoproterozoic cadomia terrane based on lithological correlations and imprecise or ambiguous isotopic data a new precise u pb date of 2061 2 ma based on analyses of single zircons for the icart granitic orthogneiss of guernsey confirms a palaeoproterozoic age of its igneous protolith the nd depleted mantle model age t dm of this gneiss is 2220 ma only slightly older than its crystallization age indicating that it represents juvenile crust other gneisses from guernsey have similar t dm ages ranging from 2210 to 2370 ma suggesting that they are also exposures of juvenile palaeoproterozoic crust a component from a penetratively deformed orthogneiss from sark previously correlated with icartian gneisses on guernsey yields a u pb zircon date of 616 4 2 ma this crystallization age demonstrates that the protolith was a cadomian intrusion and that penetrative deformation and amphibolite facies metamorphism in the northern channel islands were cadomian in age the use of gneissic features as a means of invoking the antiquity of many other undated gneissic units in the region is thus considered unreliable the presence of 2170 7 ma zircon xenocrysts within the sark orthogneiss combined with its initial e nd 615 9 5 are strong evidence that pre cadomian basement was a significant source component and that documenting the extent and age of pre cadomian basement may be possible by indirect geochemical methods

rates of processes in magmatic arcs implications for the timing and nature of pluton emplacement and wall rock deformation abstract the construction of arcs and in many cases the emplacement of plutons occur in tectonically active regions it is critical therefore to evaluate the rates of structural and magmatic processes when trying to understand the evolution of arcs and the associated pluton wall rock systems our best estimates of average rates or durations of processes in shallow to moderate level arc environments are the following 1 crystal growth rates in magma of 10 4 cm year 1 2 growth rates of metamorphic porphyroblasts between 10 5 and 10 2 cm year 1 3 long term magma supply rates of 10 1 km 3 year 1 and short term rates of up to 350 km 3 year 1 4 diapiric ascent rates for mafic plutons of 1 3 m year 1 5 cooling of plutons to ambient wall rock temperatures in 10 5 10 6 years 6 final crystallization of plutons in a small fraction of the time needed for complete cooling 7 fault displacements of 3 cm year 1 8 development of cleavages in fault zones in less than 10 6 years at strain rates of 10 13 s 1 or higher and 9 the development of regional cleavages in 10 6 years at strain rates of 10 14 s 1 these rates indicate that processes operating in magmatic arcs are relatively rapid pluton emplacement cleavage development etc occur over time spans of tens of thousands to no more than a few million years however the rate of ascent and crystallization of plutons at shallow levels is generally shorter than that needed to get large displacements on faults or widespread cleavages developed at deeper levels or in zones undergoing faster strain rates the time spans of the various processes approach one another thus plutons with otherwise similar characteristics emplaced in regions undergoing fast strain rates or at deeper crustal levels may appear quite different structurally from those emplaced at shallow levels or in regions undergoing slower strain rates comparison of these data also suggests that the rate at which wall rock deforms is the limiting factor controlling the rates of other structural processes during emplacement of plutons unless fast strain rates or multiple deformation mechanisms are considered thus emplacement mechanisms that rely on the transport of magma over 10 5 to 10 6 years are favored and need further consideration finally we argue that the structural and other characteristics of pluton wall rock systems will depend on rates of various processes involved and that these rates at the very least influence and sometimes invalidate the timing criteria previously published by us and others

immobilization of copper under an acid leach of colloidal pyrite waste rocks by a fixed bed column colloidal pyrite waste rocks cpwr which are mainly composed of colloidal pyrite and siderite widely deposit in sulfide mines in the middle and lower reaches of the yangtze river belt china especially in tongling city anhui province china in this paper a fixed bed column was used to investigate the weathering and oxidation of cpwr and its role in immobilizing low concentration cu 10 mg l 1 under weakly acidic leach ph 5 0 the experimental results indicated that the breakthrough capacity was around 14 0 mg cu g 1 cpwr when cu2 breakthrough concentration was 0 5 mg l 1 sequential extraction of cu and dithionite citrate bicarbonate extraction of free iron in the used cpwr after the column breakthrough indicated that cu removal by cpwr consisted of the following processes oxidation of pyrite and dissolution of siderite in cpwr ferrous oxidation and adsorption of cu on ferric hydr oxides this study shows the potential application of cpwr as an effective sorbent for the removal of low concentration cu from acid mine drainage

the geochemistry of rare earth elements ree in acid mine drainage from the sitai coal mine shanxi province north china abstract in this paper geochemical characteristics of rare earth elements ree in acid mine drainage amd from the sitai coal mine of shanxi province north china were investigated by determining concentrations of dissolved rees and major solutes in the amd samples concentrations of rees in the amd precipitate samples and country rock samples mudstone and coal and modeling rees species in the amd the results show that amd in the sitai coal mine have high rees and so42 concentrations in comparison with several terrestrial waters worldwide the ree speciation modeling indicates that sulfate complexes lnso4 60 and free metal species ln3 20 40 are dominant rees species in the amd amd of the sitai coal mine also shows a middle ree enriched nasc north american shale composite normalized pattern the authors suggest that both ree sulfates lnso4 in the amd and country rock of coal measures are possible reasons for middle ree enriched nasc normalized pattern of the sitai coal mine amd further work on the amd precipitates is needed to obtain more information on the origin of the middle ree enriched nasc normalized patterns