paleomagnetism of the cu zn pb bearing kupferschiefer black shale upper permian at sangerhausen germany syngenetic diagenetic and epigenetic models have been proposed for the cu zn pb kupferschiefer mineralization at sangerhausen germany paleomagnetic and rock magnetic measurements have been made on 205 specimens from mine workings on the margin of the sangerhausen syncline the mineralization is richest in the 0 5 m thick upper permian 258 2 ma kupferschiefer black marly shale nine sites and dies out over 0 2 m in the underlying weisliegend sandstones three sites and overlying zechstein carbonates two sites except for one site of fault zone gypsum characteristic remanent magnetization directions were isolated for all 14 sites using alternating field and thermal step demagnetization these directions provide a negative fold test indicating that the remanence postdates jurassic fault block tilting rock magnetic measurements show that the kupferschiefer shale marks a redox front between the oxidized weissliegend sandstones and non oxidized zechstein carbonates the 14 site directions give a late jurassic paleopole at 149 3 ma it is significantly different from the paleopole reported by e c jowett and others for primary or early diagenetic rote faule alteration that gives an age of 254 6 ma on the current apparent polar wander path and is associated with kupferschiefer mineralization we suggest that the late jurassic extensional tectonic event that formed the nearby north german basin also reactivated variscan basement faults and extended them up through the overlying strata thereby allowing hydrothermal basement fluids to ascend and epigenetically mineralize the kupferschiefer shale the possibility of a 53 3 ma mineralization age is also considered

using oxygen isotopes to establish freshwater sources in bedford basin nova scotia a northwestern atlantic fjord abstract a weekly time series of oxygen isotope 18 o measurements was collected over a 16 month period from near surface 1 m and near bottom 60 m waters of bedford basin a coastal fjord adjacent to the scotian shelf off eastern canada the time series was complemented with 18 o measurements of local precipitation rain and snow river and wastewater runoff the isotopic composition of precipitation displayed strong seasonality with an average volume weighted 18 o value of 5 39 0 96 for summer and a depleted value of 10 37 2 96 over winter winter precipitation exhibited more depleted and variable 18 o of solid precipitation relative to rainfall the annual amount weighted average 18 o of sackville river discharge 6 49 0 82 was not statistically different from precipitation 7 24 0 92 but exhibited less seasonal variation freshwater end members zero salinity intercepts estimated from annual and seasonal regressions of 18 o versus salinity s for bedford basin near surface samples were consistent with the 18 o of summer precipitation and the annual amount weighted average for the sackville river however the isotopically depleted signature of winter precipitation was not observed clearly in near surface waters of bedford basin which might reflect isotope enrichment during sublimation from accumulated snowfall prior to melting and discharge or retention and mixing within the drainage basin in near bottom waters most of the 18 o s variation average freshwater end member 7 47 2 17 could be explained by vertical mixing with near surface waters average freshwater end member 6 23 0 34 and hence with locally derived freshwater however the near bottom 18 o s variation suggested an additional contribution of a freshwater end member with a 18 o of 15 55 2 3 consistent with a remotely derived freshwater end member identified previously for the scotian shelf residuals from a long term regression of 18 o s were generally within the range expected due to analytical uncertainty 0 05 however near surface waters exhibited seasonal variability of small amplitude which was consistent with the timing and 18 o variability of local freshwater inputs

geochemical characteristics of contaminated surficial sediments in halifax harbour impact of waste discharge analyses of 274 surface sediment samples collected from halifax inlet between 1986 and 1990 permit assessment of the chemical environmental quality of this major east coast canadian harbour contamination of the marine sediments is due to discharge of untreated sewage and industrial waste directly into the harbour and leaching of solid waste deposits on land concentrations of total cu pb zn hg and cd in the uppermost 2 cm of sediments on the sea floor ranks halifax harbour among the most contaminated marine areas in the industrialized world statistical factor analysis has been used to identify five types of sediments based on sedimentological and geochemical characteristics the dominant factor type accounts for 41 of the chemical variance and represents sediments that are highly contaminated with metals and organics derived from sewage effluents and waste deposits more than 50 of the total cu zn and pb in the sediments is potentially reactive as reducible or oxidizable metal a simple two laye

rift magmatism on the eurasia basin margin u pb baddeleyite ages of alkaline dyke swarms in north greenland the opening of the arctic ocean involved multiple stages of continental rifting and intrusion of extensive dyke swarms to trace tectonomagmatic processes of the high arctic we present the first u pb ages for alkaline dyke swarms of north greenland concordia ages of 80 8 0 6 and 82 1 1 5 ma indicate that north south and east west dykes are coeval the north south dykes reflect initial east west rifting that led to break up along the gakkel ridge and formation of the eurasia basin the east west dykes reflect local variations in the stress field associated with reactivated palaeozoic faults supplementary materials u pb data are available at http www geolsoc org uk sup18857

relationship between metal enrichment and organic composition in kupferschiefer hosting structure controlled mineralization from oberkatz schwelle germany base metal mineralization is observed in some kupferschiefer localities whererote faule oxidized front of hematite bearing fluids is not present and where contemporaneous mesozoic to tertiary tectonism controlled the vein type metal enrichment processes after diagenesis structure controlled mineralization one of these localities is the spessart rhon treischfelder oberkatz schwellen region in the hessian depression germany in order to clarify the mechanism of base metal precipitation under these particular conditions a closely sampled kupferschiefer sequence from the oberkatz schwelle was investigated using organic and inorganic geochemical methods the structure controlled mineralization is enriched in as mo and u in the bottom part of the kupferschiefer and in the weissliegendes sandstones further elements such as cu ag co sb zn and pb show a redox controlled pattern of zonation in the kupferschiefer section these elements were precipitated or redistributed in the final stage of kupferschiefer mineralization participation of organic matter in base metal deposition is suggested by the depletion of h equivalents in the organic matter a similar phenomenon has been observed inrote faule controlled base metal enrichment in the north sudetic syncline of sw poland however observed differences in the composition of extractable organic matter might be due to the oxidizing potential of the migrating metal bearing fluids in the north sudetic syncline the ascending fluids were more oxidizing compared with the oberkatz schwellen area additional s content and depletion of corg are observed in the bottom section of the profile the h index hi values from rock eval analyses provide further evidence for the depletion of h equivalents in the organic matter reconstruction of the thermal regime by the measurement of vitrinite reflectance and determination of molecular rank parameters indicate a maximum temperature in the kupferschiefer of around 150 c

palaeoecology of late cretaceous polar vegetation preserved in the hansen point volcanics nw ellesmere island canada abstract mesozoic polar forests represent an extinct biome subject to a polar light regime and elevated atmospheric co2 levels in this paper new cretaceous fossil plant assemblages are reported from nw ellesmere island canada at a paleolatitude of 75 n these occur in a campanian maastrichtian aged interval of the hansen point volcanics a unit interpreted as a coastal plain peat mire complex within an active volcanic setting studies of palynomorphs sterile and fertile foliage and wood indicate that mire environments were dominated by amber producing taxodiaceous conifers with other conifers ginkgos cycads angiosperms ferns lycopsids and bryophytes occurring in subordinate numbers leaf physiognomic studies imply that most vegetation was deciduous occurrence of traumatic rings in the woods together with a high year to year variability in ring width indicates disturbed growing conditions possibly linked to a combination of frosts volcanic eruptions and flooding abundant charcoal remains indicate that an additional important disturbance process was wildfire results of this study compare closely with those from coeval circum arctic fossil sites and augment our knowledge of the community scale ecology of the cretaceous polar biome

new constraints on the age geochemistry and environmental impact of high arctic large igneous province magmatism tracing the extension of the alpha ridge onto ellesmere island canada

hydrothermal alteration of graywacke by brine and seawater roles of alteration and chloride complexing on metal solubilization at 200 degrees and 350 degrees c graywacke was reacted with seawater and with a saturated nacl brine containing ca mg and k using a solid liquid ratio of 1 10 the degree of reaction was minimal at 200 degrees c but significant at 350 degrees c in both fluids anorthite dolomite and some illite and quartz amounting to about 25 percent of the graywacke were converted to smectite chlorite and albite both fluids lost all their mg and gained k ca and co 2 only the brine gained and maintained significant concentrations of heavy metals indicating the importance of chloride complexing chloride concentration in seawater is apparently insufficient for extensive complexing under the experimental conditions chloride complexing however serves only to maintain metals in solution and prevents their reprecipitation as alteration products alteration involving production and consumption of hydrogen ions is required for the release of metals from the source matrix in the experiments mg metasomatism and dedolomitization provided the h super for the process metal solubilization by the brine followed the order of abundance in the graywacke zn ni cu pb sb cd suggesting a common matrix and no selective leaching effect in other words as a given increment of rock was altered all of its component metals were released metal concentration in solution therefore was not limited by sulfide solubility and represents minimum values changes in the bulk composition of the graywacke were minimal except for increases in mg content and the final rock would probably not be recognized as an altered source rock in the field the fluids generated during the experiments would likely subject wall rock at the site of ore deposition to hydrolytic alteration including potassium metasomatism

the early cretaceous barents sea sill complex distribution 40ar 39ar geochronology and implications for carbon gas formation abstract mafic igneous rocks of cretaceous age 80 130 ma scattered around the arctic ocean are commonly referred to as the high arctic large igneous province halip we have mapped out the distribution of halip igneous rocks in the barents sea region over the past decade based on integrated seismic gravity magnetic interpretation field work review of publications and analyses of new and vintage borehole and field samples the mapping reveals abundant igneous rocks in the northern and eastern barents sea covering an area of 900 000 km2 with a conservative volume estimate of 100 000 to 200 000 km3 of intrusions the igneous province is dominated by sheet intrusions injected into triassic and permian sedimentary rocks hydrothermal vent complexes are rare and only two potential vent complexes have been identified on seismic data in the eastern barents sea we have further done extensive radiometric dating of the igneous samples in the barents sea region new 40ar 39ar dating of thirteen samples from svalbard reveal ages of crystallization and alteration the large age span 60 140 ma for the raw ages is likely due to partial or complete overprint of the k ar system in plagioclase and the age of the magma emplacement is better represented by u pb tims ages only one of our 40ar 39ar analyses of plagioclase yielded a statistically valid age that is in line with the recently published u pb tims ages of 122 125 ma the new data clearly document that relying on published data from the k ar system can lead to erroneous conclusions on the age of crystallization in this province without a careful use of additional 40ar 39ar degassing data i e k ca we propose that the magmatism on svalbard and franz josef land represents a distinct magmatic event near the barremian aptian boundary 125 ma in the barents sea this early cretaceous barents sea magmatism resulted in the formation of the bssc barents sea sill complex bssc age rocks are also present in arctic canada sverdrup basin and on bennett island new siberia islands the massive injection of hot magma into potentially organic rich sediments in the eastern and northern barents basin caused rapid organic matter maturation and formation of thermogenic gas and oil in contact aureoles we estimate that up to 20 000 gt of carbon were potentially mobilized corresponding to 175 trillion barrels of oil equivalent the production rates and fate of the carbon gases are uncertain however we speculate that rapid release of aureole greenhouse gases methane may have triggered the oceanic anoxic event 1a oae1a and the associated negative 13c excursion in the early aptian some of the methane may also be trapped in the vast hydrocarbon gas accumulations found in the east barents basin

middle jurassic to early cretaceous igneous rocks along eastern north american continental margin late middle jurassic and early cretaceous mafic dikes sills flows and local volcaniclastic sediments are intercalated within continental shelf sediments from the baltimore canyon trough northward to the grand banks of newfoundland the igneous rocks on the eastern north american margin are mainly alkali basalts of intraplate affinity the late middle jurassic igneous activity was of short duration at about 140 ma and was restricted to georges bank where it led to construction of several volcanic cones the main period of igneous activity was concentrated at about 120 ma in the aptian barremian the activity consists of dike swarms in baltimore canyon occasional dikes on the scotian shelf and the growth of stratovolcanoes on the scotian shelf and grand banks younge dikes 95 ma also are present on the grand banks the major phases of igneous activity are synchronous with major regional tectonic events namely the initiation of rifting in the labrador greenland region 140 ma separation of continental plates between iberia and the grand banks 115 ma and separation of labrador and greenland continental plates 83 92 ma most of the igneous activity occurred along old fracture zones that appear to have been reactivated and or along fractures or fracture zones in the continental crust resulting from changes in stress patterns caused by plate motion the co occurrence of middle jurassic and early cretaceous volcanic activity on the continental slope off georges bank is evidence that a hot spot process alone cannot explain the linear character and age trends within the new england seamounts propagation of a fracture zone into oceanic crust more satisfactorily accounts for the age and distribution of the volcanism with regard to oil exploration on the continental margin care must be taken to properly identify igneous and volcaniclastic rocks on mechanical logs drill cuttings and cores reflection seismic profiles can be used to map the areal extent of sills flows and low angle dikes which commonly show distinctive seismic responses however steeply dipping dikes generally produce little if any seismic response isotopic age determinations of igneous rocks combined with biostratigraphic age determinations of adjacent strata are invaluable for stratigraphic correlation establishing chronology of seismic sequences and analysis of basin sedimentation and tectonic history

biogenic origin of intergrown mo sulphide and carbonaceous matter in lower cambrian black shales zunyi formation southern china abstract the lower cambrian zunyi formation in southern china hosts complex intergrown phases of mo sulphides and anthracite like carbonaceous matter and graphite mosc pyrite and ni sulphides these sulphides occur in a few centimeters thick polymetallic stratiform layer in black shales above phosphorites cherts dolomites and barite the ore horizon contains 7 wt mo 2 wt ni 19 wt s and 13 wt c org and c tot co 2 58 wt 14 wt cao 1 2 wt as 2000 ppm se 5400 ppm zn 450 ppm u and v and up to 1 ppm platinum group elements three types of mosc phases always including framboidal pyrite are distinguished 1 rounded structures few hundred microns large 2 relict inclusions in diagenetic pyrite 3 grains interstitial to sulphurised and phosphatised organic matter at the nanoscale mosc is represented by nanometric porous rounded structures of mos 2 finely intergrown with carbonaceous matter of typical nano onion structures mosc also contains nanocrysts of quartz clays ca sulphate carbonate and ni sulphides micro raman spectroscopy shows that the carbon phase has a maturation grade of anthracite indicating temperatures below 300 c mosc is mainly composed of 25 wt mo 23 wt s 5 6 wt fe 2 5 wt ni 33 wt c 1 5 wt o 0 6 wt n and several hundreds of ppm of cu as se sb pd zn co and sn electron energy loss spectra show that n is related to nanosized carbonaceous matter the mean c n ratio 57 of mosc is similar to those observed in marine organic matter and those reported from zooplankton at hydrothermal vents the mineralized shales are crosscut by hydrothermal veins composed of carbonate or barite always associated with quartz apatite and fe and zn sulphides a paragenesis also observed as nanocrysts in mosc although mo originated from seawater its extreme concentration is due to an enhanced growth of bacterial consortia in a diffuse hydrothermal vent system these consortia may be dominated by nitrogen fixing and mo dependant hyperthermophilic or mesophilic species containing nitrogenase composed also of mo s fe organic matter decay led thus to the formation of mosc and the included framboidal pyrite

new data from halifax harbour paleoenvironment and a new holocene sea level curve for the inner scotian shelf two vibracores collected from halifax harbour allow reevaluation of the early postglacial history and part of a new sea level curve for eastern nova scotia an acoustically distinct seismic unit fo

genesis of copper lead mineralization in the regionally zoned agnigundala sulfide belt cuddapah basin andhra pradesh india shallow marine sandstone shale carbonate sedimentary rocks of the paleoproterozoic northern cuddapah basin host copper nallakonda deposit copper lead dhukonda deposit and lead mineralization bandalamottu deposit which together constitute the agnigundala sulfide belt the cu sulfide mineralization in sandstone is both stratabound and disseminated and pb sulfide mineralization occurs as stratabound fracture filling veins and or replacement veins within dolomite systematic mineralogical and sulfur carbon and oxygen isotope studies of the three deposits indicate a common ore fluid that deposited copper at nallakonda copper lead at dhukonda and lead at bandalamottu under progressive cooling during migration through sediments the ore fluid was of low temperature 200 c and oxidized thermochemical reduction of basinal water sulfate produced sulfide for ore deposition it is envisaged that basal red bed and evaporite bearing rift related continental to shallow marine sediments might have acted as the source for the metals rift related faults developed during sedimentation in the basin might have punctured the ore fluid pool in the lower sedimentary succession and also acted as conduits for their upward migration the ore bearing horizons have participated in deformations during basin inversion without any recognizable remobilization

a chronology of natural and anthropogenic influences on coastal sedimentation new zealand 14c and 137cs chronologies of sediment accumulation were obtained from five sediment cores taken from wellington harbour new zealand a 10 000 year chronology records the holocene transgression european colonisation and variations in the general sediment accumulation rate caused by earthquake uplift and anthropogenic activity rates vary from a high of 60 to a low of 0 1 mm a 1 in general rates increased at the beginning of the holocene marine transgression but by 5000 yr bp they reached a stable level harbour wide these rates remained stable until the second half of the 19th century when deforestation by european settlers caused order of magnitude increases in sediment accumulation in the past 40 80 years rates have increased again as a result of urban growth and river channel management although the effects are less pervasive harbour wide influences can be placed in two categories natural and anthropogenic the latter being recent contributions to a sedimentary regime dominated by the holocene marine transgression sediment accumulation rates indicate that two major earthquake uplift events had only a local effect on harbour sediments anthropogenic influences are considered to be more significant sedimentologically than earthquake activity

late cretaceous bimodal magmatism northern ellesmere island isotopic age and origin in the yelverton bay region of northwestern ellesmere island bimodal intrusive and volcanic rocks are associated with a major fault in the proterozoic cambrian rocks of the pearya terrane the wootton intrusion consists mainly of gabbro with lesser amounts of granitic and hybrid rocks the hansen point volcanics are composed of felsic rocks and basalt plutonic zircons are very slightly discordant but volcanic zircons have unusually high degrees of inheritance interpreted u pb zircon ages of 92 0 1 0 ma for the wootton intrusion assuming a wide range of inheritance ages and of for the hansen point volcanics are close to the 93 ma average of hornblende k ar dates obtained earlier for a small quartz diorite pluton in central northernmost ellesmere island all fall into the early late cretaceous and indicate correlation with mafic volcanics of the cenomanian turonian strand fiord formation of eastern axel heiberg island the upper intercept age for the hansen point volcanics suggests that the felsi

princess margaret arch re evaluation of an element of the eurekan orogen axel heiberg island arctic archipelago it is argued on the basis of structural stratigraphic and sedimentologic criteria that princess margaret arch developed during the principal phase of eurekan thrusting and folding and therefore is no older than middle eocene sub eureka sound group unconformities on eastern axel heiberg island are not associated with uplift on the eastern flank of this arch but are related to erosion of mesozoic sverdrup basin strata over local evaporite diapir domes and ridges considerable disparity exists between levels of erosion on the flanks of the arch and the level of erosion along its axis which cannot be explained by pre eocene uplift sedimentary facies and textural and petrographic characterisitics of eureka sound group strata do not reflect proximity to an arch palynomorph assemblages in the west derived syntectonic buchanan lake formation middle eocene contain reworked latest cretaceous spores and pollen that were derived from eureka sound group strata originally located on or close to the arch axis e

mineralogy and trace element relative solubility patterns of shallow marine sediments affected by submarine tailings disposal and artisanal gold mining buyat ratototok district north sulawesi indonesia shallow marine sediments of the buyat ratototok district of north sulawesi indonesia are affected by submarine disposal of industrial gold mine tailings and small scale gold mining using mercury amalgamation industrial mine tailings contained 590 660 ppm arsenic 490 580 ppm antimony and 0 8 5 8 ppm mercury electron microprobe survey found both colloidal iron arsenic phases without sulphur and arsenian pyrite in tailings and sites to which tailings had dispersed but only arsenopyrite in sediments affected by artisanal mining antimony in tailings was present as antimony oxides colloidal iron antimony phases colloidal iron antimony phases and stibnite in sediments affected by both types of mining a sequential extraction found that 2 of arsenic held in tailings and tailings contaminated sediments was exchangeable 20 30 was labile including weakly adsorbed carbonate and arsenate bound 20 30 was metastable probably incorporated into iron or manganese oxyhydroxides or strongly adsorbed to silicate minerals and 40 48 was relatively insoluble probably incorporated into sulphides or silicates arsenic in sediments affected by artisanal gold mining was 75 95 relatively insoluble antimony in all sediments was 90 relatively insoluble relative solubility patterns of most other metals did not differ between industrial tailings affected artisanal mining affected areas and fluvial sediments results suggest that submarine tailings disposal is not suitable for refractory carlin like gold deposits because ore processing converts arsenic to forms unstable in anoxic marine sediments

metal accumulation during and after deposition of the kupferschiefer from the sangerhausen basin germany abstract a densely sampled profile 58 cm in thickness composed of 13 samples of the kupferschiefer and overlying zechstein carbonates from the sangerhausen basin germany has been analysed by various geochemical and microscopic methods in order to clarify the mechanism of base metal accumulation in this location the kupferschiefer is only slightly influenced by the hematite bearing oxidized fluids called rote faule the determination of facies dependent parameters along the profile indicates that kupferschiefer from the sangerhausen basin was largely deposited in a marine environment only at the beginning of kupferschiefer sedimentation did euxinic conditions prevail the bottom part of the profile is significantly enriched in trace elements such as cu ph zn as co ag and u the cu concentration amounts to 19 88 wt post depositional oxidation of the organic matter is observed only in the transition zone between the kupferschiefer and the zechstein conglomerate indicating the influence of ascending oxidizing brines microscopic analyses show that only fe sulfides form framboidal textures cu minerals are present along the total profile preferentially in fractures and as patchy structures composed of chalcocite chalcopyrite and bornite in the highly mineralized bottom section cu sulfides are associated with pyrobitumen sparry calcite and arsenopyrite results from maturation studies of organic matter suggest that the maximum temperature affecting the kupferschiefer was approximately 130 c a 3 step process of metal accumulation is proposed during deposition of the sediment framboidal pyrite and pyrite precursors were precipitated by bacterial so 4 2 reduction bsr during diagenesis the pyrite and pyrite precursors were largely replaced by mixed cu fe minerals and by chalcocite pr in the section with very high cu contents 8 reduced sulfur from fe sulfides was not sufficient for precipitation of cu and other trace metals from ascending solutions in this part of the profile thermochemical so 4 2 reduction tsr occurred after pyrite replacement as indicated by the presence of pyrobitumen and sparry calcite

experimental study of the formation of chalcopyrite and bornite via the sulfidation of hematite mineral replacements with a large volume increase chalcopyrite cufes2 and bornite cu5fes4 are the most abundant cu bearing minerals in hydrothermal cu deposits forming under a wide range of conditions from moderate temperature sedimentary exhalative deposits to high temperature porphyry cu and skarn deposits we report the hydrothermal synthesis of both chalcopyrite and bornite at 200 300 c under hydrothermal conditions both minerals formed via the sulfidation of hematite in solutions containing cu i as a chloride complex and hydrosulfide at ph near the pka of h2s aq over the whole temperature range polycrystalline chalcopyrite formed first followed by bornite assuming that fe behaves conservatively the transformation of hematite to chalcopyrite involves a large increase in volume 290 the reaction proceeds both via direct replacement of the existing hematite and via overgrowth around the grain chemical exchanges between bulk solution and hematite are enabled by a network of micrometer size pores however in some cases the chalcopyrite overgrowth develops large grain sizes with few apparent pores and in these cases fluid transport may have been via a network of fractures similarly to the replacement of hematite by chalcopyrite bornite forms via the replacement of chalcopyrite the reaction has a large positive volume 230 and proceeds both via chalcopyrite replacement and via overgrowth this study shows that replacement reactions can proceed via coupled dissolution reprecipitation even where there is a large volume increase between parent and product mineral this study also provides further evidence about the controls of reaction pathways onto the final mineral assemblage in this case the host initial fluid was undersaturated with respect to fe bearing minerals upon slow release of fe at the surface of hematite a mineral assemblage of chalcocite bornite and finally chalcopyrite is expected however in practice chalcocite did not nucleate on the surface of hematite rather relatively slow nucleation of bornite enabled high concentrations of fe to build up near the dissolving hematite so that chalcopyrite high sulfidation experiments or chalcopyrite pyrite low sulfidation crystallized first

geochemistry of the kupferschiefer poland cu pb and zn are the main metals occurring in sulfides in the kupferschiefer they are arranged in the three distinct zones around rote faule in the order cu pb and zn copper zones are enriched in transition metals i e ag ni co v and mo ranging from 600 to 1500 ppm they are concentrated especially in the bottom part of black shale re is associated with mo the re mo ratio in cu pb and k castaingites is about 1 70 in copper zones near the contact with lead zones au platinum group metals pgm and u are concentrated ranging from traces to several hundred ppm the main mechanism of concentration of transition metals was catalytic autooxidation and dehydrogenation of organic matter the noble metals form either independent minerals or are present in organic matter and thucholite in the lead zones at the contact with cu zones an increased content of ag 100 1500 and hg 5 800 ppm is present the average hg content for the black shale of the zone is 61 ppm a natural gas exploited from the rotliegendes beneath the kupferschiefer carries in aerosols significant amount of pb cu mn fe ag and hg this suggests the rotliegendes as a pathway or as a source of metals for the kupferschiefer the presence of k castaingite intergrown with silvinite kcl may suggest k dominated brines as the mineralizing fluids

the eurekan deformation in the arctic an outline the evolution of the eurekan deformation zones in the arctic is closely related to the development of the circum greenland plate boundaries in early cenozoic times 53 34 ma mostly the eurekan orogeny or deformation has been interpreted as a predominantly compressive tectonic event but the eurekan deformational history in the arctic was not the result of a single tectonic episode it rather represents a complex sequence of successive tectonic stages which produced a number of intra continental deformation zones with changing sometimes opposing lateral oblique and convergent kinematics in the canadian arctic archipelago north and ne greenland and svalbard the interaction between the continental plates especially in combination with the development of transform faults resulted onshore in the formation of several complex deformation zones and areas of eurekan deformation the eurekan deformation can be divided into two major tectonic stages the first phase in the early eocene was dominated by orthogonal compression in the west spitsbergen fold and thrust belt along the west margin of the barents shelf and contemporaneous sinistral strike slip tectonics along the wegener fault and on ellesmere island whereas the second phase in the late eocene was characterized by dextral strike slip and compression on ellesmere island and contemporaneous dextral transpression and transtension along the de geer fracture zone or hornsund fault complex between ne greenland and spitsbergen

polymetallic mineralization at the browns deposit rum jungle mineral field northern territory australia the rum jungle mineral field northern territory australia forms part of the paleoproterozoic pine creek orogen the geology of the area comprises two archean granitic basement domes overlain by a paleoproterozoic sequence of metasedimentary and subordinate metavolcanic rocks the rocks have been deformed and metamorphosed to greenschist facies during the 1880 ma barramundi orogeny but the original stratigraphic succession has been preserved the browns deposit browns and its extension browns east hosted within black carbonaceous pelites of the paleoproterozoic whites formation is the largest base metal deposit found to date in the pine creek orogen present resource estimates are 39 million metric tons mt at 0 44 percent cu 3 61 percent pb 0 11 percent co and 0 09 percent ni browns and 31 mt at 1 29 percent cu 1 28 percent pb 0 13 percent co and 0 13 percent ni browns east major sulfide minerals in the ore zone are galena sphalerite chalcopyrite pyrite and the main carrier of ni and co siegenite ni co 3 s 4 digenite group minerals and bornite ca bearing plumbogummite pbal 3 po 4 2 oh 5 h 2 o arsenopyrite and gersdorffite are present in minor quantities ore minerals occur as fine grained wisps parallel to the main bedding parallel foliation and as coarse grained mono and polyminerallic aggregates that crosscut the foliation total noncarbonate carbon contents of unaltered rocks range from 1 07 to 7 51 wt percent total sulfur contents range from 2 13 to 6 14 wt percent petrographic studies and raman spectroscopy identify three varieties of carbonaceous matter primary syngenetic premetamorphic epigenetic grain coating and postmetamorphic epigenetic uraniferous migrated altered rocks are rarely encountered values of 34 s for sulfides range from 5 to 15 per mil and are interpreted to reflect a combination of inorganic thermochemical reduction of seawater and bacterial activity no specific sulfur isotope patterns for individual minerals can be established indicating nonequilibrium conditions homogeneous lead isotope signatures of galena 206 pb 204 pb 16 20 16 22 207 pb 206 pb 15 48 15 51 208 pb 207 pb 35 86 35 92 suggest that all pb was derived from a single crustal source and paragenetically late crosscutting galena appears to have been remobilized from bedding parallel galena despite the occurrence of uranium in similar rocks nearby uranium is quantitatively insignificant in the browns deposit and is not genetically related to base metal mineralization instead it is linked to brittle deformation in the waning stages of orogenesis the browns deposit differs from other well known sediment hosted stratiform ore deposits both the zambian copperbelt and the polish kupferschiefer deposits are copper dominant and hosted in sedimentary sequences with significant psammitic components the pb zn ag deposits of the proterozoic australian zinc province also have significant carbonate in their host rocks e g carbonaceous dolomitic and siltstone at mcarthur river and lack economically interesting cu co and ni the nearby woodcutters pb zn ag deposit in rocks of similar age also differs in structural setting veins dominant metals and pb isotopes from the browns deposit

accumulation of contaminant metals in marine sediments of halifax harbour nova scotia environmental factors and historical trends abstract sediments in halifax harbour have accumulated contaminant metals hg cu zn and pb as a result of discharge of untreated sewage and industrial waste leaching of land fill waste and surface drainage concentrations of contaminants in210pb dated sediment cores became significant about 1880 and rose rapidly after 1900 reaching maximum concentrations in the decades between 1950 and 1980 mean concentrations of hg increased from 0 2 g g 1 in pre 1890 sediments to 1 6 g g 1 in the 20th century similar enrichments for cu changed the concentration from 26 to 88 g g 1 for zn from 90 to 250 g g 1 and for pb the increase was from 12 to 206 g g 1 statistical factor analyses of geochemical data have been used to identify 1 primary contaminants directly associated with waste discharge these include total and organic bound forms of cu zn and pb 2 secondary contamination attributed to leaching and modification of primary contaminants include acid labile forms of zn ni and cu 3 diagenetic modification of buried sediments are identified by total and labile forms of mn 4 dispersion of contaminants from land surface drainage are characterized by fine grained aluminosilicates historical trends in the changing dominance of these environmental factors reflect changes in industrial activity urban growth and changes in the use of metals in paints domestic and industrial chemicals and in the combustion of fuels

gravity and magnetic modelling of layered mafic ultramafic intrusions in large igneous province plume centre regions case studies from the 1 27 ga mackenzie 1 38 ga kunene kibaran 0 06 ga deccan and 0 13 0 08 ga high arctic events gravity and magnetic data from the global egm2008 and emag2 datasets are used to identify geophysical anomalies in large igneous province lip plume centre regions with the goal of characterizing mafic ultramafic intrusions linked to those lips geophysical anomalies within 18 lips distributed globally are investigated four of these lips are selected for detailed modelling the 1 27 ga mackenzie 1 38 ga kunene kibaran 0 06 ga deccan and 0 13 0 08 ga high arctic lips we recognize three spatial distribution types for intrusions in plume centre regions these are 1 intrusions emplaced along a circular fault system that circumscribes the plume centre 2 intrusions emplaced along linear rifts that in some cases converge towards the plume centre and 3 single or unclassified intrusions modelling supports that the geophysical anomalies associated with these lips tend to be produced by large radius 30 km and deep seated crustal intrusions with densities consistent with mafic ultramafic rock and

meta evaporite sequence exhalative chemical sediments and associated rocks in the proterozoic willyama supergroup south australia implications for metallogenesis abstract the willyama supergroup comprises proterozoic meta sedimentary and meta igneous rocks in western new south wales and eastern south australia and contains the giant broken hill pb zn ag deposit in addition to numerous small stratiform stratabound and vein mineral deposits new lithological geochemical and fluid inclusion data from the olary block west of broken hill suggest the presence of former evaporite rocks now metamorphosed to a variety of chemically and mineralogically unusual lithologies these evaporite rocks overlie relatively oxidised strata and are in turn overlain by reduced graphite bearing pelites rocks of sodic composition abound represented by albite quartz rich rocks calcite actinolite epidote garnet clinopyroxene inferred to represent metamorphosed analcime rich strata of felsic volcaniclastic provenance with variable proportions of carbonates for example calcite dolomite trona and shortite these rocks are interspersed with potassic rocks possibly also with an evaporitic origin in addition to normal clastic meta sediments the presence of halogen rich minerals in a distinctive mineral assemblage hypersaline fluid inclusions pseudomorphic voids and minerals after gypsum and carbonate in addition to tourmalines with isotopically light boron isotopes is interpreted as evidence for a non marine evaporite parent rock for portions of the olary block types of mineral occurrences in the olary block form a continuum between chemical sediments formed by the exhalations of hydrothermal fluids to intrasediment deposits inferred to have been formed due to the chemical changes imposed on these and or diagenetic fluids during their passage through the sedimentary pile disseminated stratabound pyrite including cobaltian types and chalcopyrite extend along strike for many kilometres and are interpreted to have formed by a diagenetic mechanism the presence of massive sulphide bearing strata iron formations barite tourmalinite and manganiferous rocks are typical of chemical sediments derived from hot spring sources the olary block meta evaporites have similar whole rock compositions to tertiary analcime rich rocks of the green river formation wyoming these new data imply that portions of the adjacent broken hill block may also comprise meta evaporites for example the quartz albite rich strata of the thackaringa group and the calcsilicates of the lower broken hill group and that the disseminated cobaltian pyrite mineralisation in the thackaringa group may not be of exhalative origin

pristane phytane ratios in the mineralized kupferschiefer of the fore sudetic monocline southwest poland abstract the interaction of organic matter with fluids is important in geochemical processes in surface and diagenetic environments in the kupferschiefer copper deposits of southwestern poland organic fluid interactions are inferred to have been important in the genesis of the ore deposits previous organic geochemical studies of the kupferschiefer report evidence of a late diagenetic oxidation event that altered the organic geochemistry this study uses the saturated hydrocarbons as indicators of the biological input and the earliest diagenetic processes to affect the organic geochemistry of the kupferschiefer the normal alkane distributions are lithofacies controlled indicating that they reflect biological input the ratio of the saturated isoprenoids pristane phytane are potential indicators of the redox conditions during sedimentation and diagenesis very low pr ph ratios are associated with lithofacies that were deposited in hypersaline environments increases in the pr ph ratio within individual traverses are interpreted as indicating increasing oxidation of organic matter during deposition and early diagenesis trends of increasing pristane phytane ratios are observed at the base of the kupferschiefer and at the transition within the kupferschiefer from the clay rich to the carbonate rich kupferschiefer which corresponds approximately to the transition from cu zone to the pb zone early diagenetic copper depleted cu and cu fe sulfides have also been reported form the top of the weissliegendes and the cu zone pb zone transition and it is conceivable that both could be related to the same processes

accumulation of copper in the permian kupferschiefer a result of post depositional redox reactions abstract within the central european zechstein basin the permian kupferschiefer has been deposited under anoxic conditions in most parts of the basin the metal content does not exceed values commonly observed in black shales however in areas near to the zechstein sea shore which are simultaneously related to rift zones a significant base metal enrichment is observed organic geochemical analyses of the copper mineralized sections in the kupferschiefer from southwest poland show that significant changes in the composition of organic matter are associated with the metal enrichment processes porphyrins commonly abundant constituents of the shale have been decomposed by oxidizing fluids additionally aliphatic hydrocarbons have been largely removed from the bitumen and alkylated aromatic systems were affected by side chain degradation this particular type of alteration is explained by ascending oxidizing solutions which transported high amounts of base metals from lower permian red beds into the kupferschiefer horizon acting as a geochemical trap the metal precipitation is suggested to be a result of thermochemical sulphide production with organic matter acting as hydrogen source in areas such as the lower rhine basin in the bottom section of the kupferschiefer the base metals lead and zinc as well as barium have been accumulated from basinal carboniferous formation waters copper enrichment is not observed because potential source rocks are missing in this area however the observed compositional changes of the organic matter do not point towards thermochemical redox processes

ree and their relevance to the development of the kupferschiefer copper deposit in poland abstract over one hundred samples representing mainly clayey organic and carbonate rich shales kupferschiefer but also other members of different ore sections including hangingwall dolomites z1 werra and footwall weissliegend sandstone lower permian have been collected in different mines of the lubin glogow mining district mainly near the contact transitional zone between the copper mineralized zone and secondarily oxidized rote faule rf zone in general the polish kupferschiefer shales are enriched in mree in comparison to nasc in a typical copper rich ore section the ree amounts and patterns depend on lithologies being generally similar in shales and dolomite ree vary among sandstones shales and dolomites average 73 143 and 85 ppm respectively probably reflecting mainly their clay contents sandstones have strongly convex ree patterns with positive eu and negative gd anomalies and depletion in lree and enrichment in mree relative to hree the ree patterns of shale and dolomite are similar to one another and rather flat with strong negative eu anomalies and a small positive gd anomaly in the case of shales the ree patterns of shales from the mineralized cu zone are generally convex mree enriched and have negative eu anomalies however in a section with cu zn and pb shales the ree pattern of pb bearing shales shows a positive eu anomaly in contrast to other shales and overlying dolomite more oxidizing conditions of deposition can be assumed for pb shales no significant differences between ree distributions in transitional and oxidized zones have been observed their ree patterns are more convex and are much higher av 247 ppm than those in the mineralized zone and they do not show eu anomalies the strongly convex pattern may suggest either enrichment in mree or relative depletion in lree due to localized precipitation of light ree minerals both in shales and in the uppermost part of the sandstones two unique sections one cu rich and one cu lean partly oxidized comprising three shale beds interbedded with dolomites have been compared generally ree contents are similar in these two sections also similar are changes in contents of ree between beds in both sections which decrease significantly upwards from 157 171 ppm to 54 60 ppm the ree patterns of the lowermost beds directly overlying sandstones are ramp like with lree enrichments the upper beds have concave ree patterns comparison between sections shows generally stronger negative eu and positive gd anomalies in the highly mineralized section there is a highly significant positive relationship between cu and ree contents in cu rich shales and slightly less significant negative relationship for their concentration in oxidized and transitional shales there is a moderate significant positive correlation between p 2 o 5 and ree contents in cu rich shales the observed differences in ree contents cannot be provenance dependent but have been caused by diagenetic processes possibly related to mineralization and oxidation processes europium anomalies generally reflecting different eh conditions in the deposit can be eliminated by the prolonged oxidation strong enrichment of the rf zones in ree may result from their desorption from large volumes of oxidizing including mineralizing solutions which probably emerged from the underlying molasse lithologies into the rote faule areas higher contents of ree in the lowermost shales suggest upward movement of solutions from the underlying sandstones also far away from the rf areas

a comparative study of the influence of organic matter on metal accumulation processes in the kupferschiefer from the hessian depression and the north sudetic syncline abstract the major kupferschiefer type ore deposits are located in the proximity of the saxothuringian rhenohercynian border zone at the southern border of the former central european zechstein basin previous studies primary carried out on kupferschiefer from the north sudetic sydetic syncline in southwest poland konrad mine provided evidence that organic matter om is of major importance for the mineralizing events in the copper bearing zone thermochemical sulfate reduction was regarded to be the major process providing reducing equivalents for the precipitation of base metal sulfides the present study has been carried out in order to investigate whether this process can also be responsible for other high grade kupferschiefer deposits such as those known from the hessian depresssion germany although here the degree of base metal accumulation is much lower in comparison to the one observed in the polish mining districts results from kerogen analyses using the methods of coal petrology indicate that in both mining areas the maturation of the organic matter is not related to the degree of metal enrichment in the kupferschiefer palaeogeographical criteria such as the location of the redox boundary known as rote faule appear to be the predominant controlling factors for the base metal enrichment measurements of the spectral fluorescence of total extracts of kupferschiefer reveal differences in the composition of extracts comparing samples from the hessian depression and the north sudetic syncline in the north sudetic syncline fluorescence intensities increase and the maximum wavelengths decrease near the rote faule in the hessian depression richelsdorf area the opposite trend is observed this difference can be explained by the addition of strongly fluorescing compounds from the carboniferous basement in the north sudetic syncline together with the fluids controlling the rote faule distribution a possible source for these compounds is apparently missing in the basement of the hessian depression this is reflected by the comparative organic geochemical investigations of two sample sets from the hessian depression and the north sudetic syncline the major difference is the abundance of polycyclic aromatic hydrocarbons pah and polycyclic aromatic sulfur hydrocarbons pash in vicinity of the rote faule only in the samples from the north sudetic syncline the same set of compounds is absent from the oxidized zones in the hessian depression

cenomanian to santonian radiolarian biostratigraphy carbon isotope stratigraphy and paleoenvironments of the sverdrup basin ellef ringnes island nunavut canada abstract an upper albian to santonian sedimentary record on ellef ringnes island canadian arctic archipelago records variable paleoenvironmental conditions within the cretaceous polar sea and sverdrup basin the upper albian to lower cenomanian uppermost christopher and hassel formations represent a regressive system tract from offshore to shoreface terrestrial paleoenvironments the upper cenomanian to santonian shales of the kanguk formation signify a distal offshore basin setting controlled by increased subsidence and high global sea levels siliceous pelagic faunas and floras dominate the basin and herein three informal radiolarian partial range zones are proposed for the polar sea alternating diversity and abundance patterns are interpreted as a response to sea level controlled productivity systems transgressive phases correspond to low diversity shallow dwelling radiolarian taxa with an expanded oxygen minimum zone omz regressive phases are coupled with radiolarian radiations of deeper dwelling species and a depressed omz the upper cenomanian to turonian was marked by increased preservation of marine type organic matter and organic carbon isotope excursions indicate the presence of the oceanic anoxic event 2 oae 2 at the base of the kanguk formation rock eval data suggest that an increasing terrestrial influence prevailed during the coniacian to campanian time covering the oae 3 benthic environments are dominated by anoxic conditions as suggested by the near lack of benthic foraminifera and extensive intervals of fine platy shale lacking bioturbation only the upper coniacian records a return to dysoxic benthic conditions radiolarian faunal comparisons to more southern localities suggest migration routes from the east through a narrow north atlantic pathway and from the pacific through the alaskan asian pathway

origin of the gold deposit in the polkowice west mine lubin sieroszowice mining district poland the recently discovered gold deposit in the lubin sieroszowice district lies 0 0 to 1 5 m below the stratabound copper silver orebody mainly in the polkowice west mine the deposit extends over 60 km2 has a thickness of 20 80 cm and a conservative estimate of the average grade of 1 5 g t gold 0 3 g t pd and 0 2 g t pt it contains gold and electrum in association with minor amounts up to 0 4 vol of hematite chalcocite digenite djurlite bornite chalcopyrite pyrite gersdorffite rammelsbergite and clausthalite the gold bearing zone lies mainly in the weissliegendes sandstone but locally transgresses the stratigraphy into the overlying kupferschiefer shale and werra dolomite of the zechstein evaporite sequence it lies within a transition zone between the oxidized hematite stained rote faule facies and the overlying reduced organic carbon bearing sediments at the polkowice west mine but only where gold is present this zone is characterized by hematite stained patches within grey to maroon sediment that contains little or no hematite or organic carbon these textures were caused by downwelling reducing sulfur rich solutions flowing through previously oxidized sediments and by gravitational instability between the reducing and oxidizing fluids the oxidizing fluid originated within the rote faule facies whereas the reducing fluid originated in the overlying zechstein sequence from which it was expelled downward during gypsum dehydration accompanying burial gold transport as the chloride complex in the oxidizing fluid is unlikely at the low temperature 100 c prevailing during mineralization some gold was probably transported as the bisulfide and to a lesser extent the polysulfide complexes in the descending reducing fluid however the potential source rocks do not contain enough gold to account for the known deposit most of the gold was probably transported as the thiosulfate complex during replacement of reduced sediments by the rote faule facies parts of the district where reduced fluids penetrated deeply into the weissliegendes and where the rote faule facies transgressed the greatest volume of reduced sediments should be evaluated for the presence of gold we propose that the polkowice west mine represents a new class of gold deposit

diffusion and reaction controlled cu pb zn ore mineral precipitation in a reducing system a model applied to the pattern of ore mineral precipitation in the kupferschiefer and other black shales the major ore minerals in black shale hosted copper deposits typically have a zoned distribution in this paper a numerical model that couples the processes of chemical reaction and interdiffusion of metals and sulfur is applied to reproduce the pattern of mineral precipitation in a reducing black shale environment the results indicate that under reducing conditions discrete regions of sulfide precipitation develop and with time these regions evolve toward the source of the metals the model shows that the observed spatial distribution of the different sulfides may be a consequence of reaction and diffusive supply of metals and sulfur rather than changes in eh although this result does not prove that variations in eh and ph were not responsible for the zoned mineral distribution in black shales it does illustrate the need to consider reactive transport modeling when one attempts to model ore deposition in black shales comparison of these results with published data on the kupferschiefer black shale hosted copper deposits reveals a number of similarities including a similar pattern of sulfide distribution and the same sense of asymmetry in plots of sulfide concentration vs distance

organic geochemistry and mineralogy i characterisation of organic matter associated with metal deposits abstract as geochemical appraisals of mineral regions of commercial prospectivity evolve the organic matter associated with metal rich ores has attracted greater attention petroleum basin and modern seafloor hydrothermal vent studies have suggested that organic matter can have a significant influence on the behaviour of mineralising fluids there have been many isolated reports of certain organic compositional or morphological e g pyrobitumen features showing an apparent relationships with hydrothermal fluids or minerals raising expectations that organic based parameters might be useful to mineral exploration however the understanding of organic inorganic relationships in earth systems is far from complete for example the detailed mechanics of the interaction of organics with hydrothermal fluids over geological time remain largely undefined organic geochemistry studies have traditionally involved the measurement and interpretation of the hydrocarbon composition of sedimentary rocks here we review the types of aliphatic hydrocarbons aromatic hydrocarbons and metalloporphyrins often detected from organic geochemical investigations in mineral rich regions such molecular data can be particularly diagnostic of biochemical sources and the palaeo environments at the time mineral associated organic matter was deposited sub surface trends of hydrocarbon alteration may also reflect major biogeochemical processes such as thermal maturity and biodegradation organic geochemistry data can also occasionally provide information about the nature e g origin composition temperatures and migration pathways of hydrothermal fluids and can make a contribution to holistic ore genesis models the well preserved organic matter associated with the economic here s your chance pb zn ag mine paleoproterozoic barney creek formation mcarthur basin australia and the transition metal rich early permian kupferschiefer formation germany poland have attracted significant attention a more detailed summary of the organic character of these deposits is provided to highlight the contribution organic geochemistry can make to understanding mineralisation processes most organic geochemical studies of highly mineralised regions however have not adequately addressed the significance of organic matter to mineralisation a slightly different analytical focus than traditionally used for exploration appraisal of petroleum hydrocarbons may be required to properly evaluate the significance of organic species to the mobilisation transport and deposition of ore metals the characterisation and subsequent thermodynamic modeling of organic substances and complexes within metalliferous hydrothermal systems will contribute to a better understanding of the nature and role of organic inorganic fluids or other affiliated organics in ore systems

the permian kupferschiefer of southwest poland a geochemical trap for migrating metal bearing solutions abstract the ore grade cu mineralization in southwest poland is associated with the presence of the rote faule zone that overlies the contact of saxothuringian and rhenohercynian zones in these areas the soluble organic matter in the kupferschiefer is altered strongly saturated hydrocarbons and alkylated aromatic compounds are depleted significantly in comparison to non altered shale samples of a similar maturation instead unsubstituted di and tricyclic aromatic hydrocarbons are the dominant components of the extractable bitumen the observed alteration points to late diagenetic oxiadtion reactions caused by upward migrated metalliferous solutions moreover polycyclic aromatic hydrocarbons pah associated with polycyclic aromatic sulphur hydrocarbons pash are abundant in some samples these compounds are considered to originate from the underlying carboniferous strata and were carried upward to the kupferschiefer zone which acted as a geochemical trap

redox fluctuations trace metal enrichment and phosphogenesis in the 2 0 ga zaonega formation abstract the 2 0 ga zaonega formation zf holds one of the oldest phosphorites in the geologic record reaching 15 p2o5 understanding the depositional conditions that enabled sedimentary phosphorus enrichment in this unit will thus help us to interpret the significance of the temporal distribution of phosphorites in earth s early history here we use an array of major and trace element data to constrain the redox conditions in the water column and extent of basinal restriction during deposition of the zf we also present new selenium se abundance and isotopic data to provide firmer constraints on fluctuations across high redox potentials which might be critical for phosphogenesis we find that se isotope ratios shift over a range of 3 in the zf with the earliest stratigraphically resolved negative se isotope excursion in the geologic record implying at least temporarily suboxic waters in the basin furthermore we find that redox sensitive element rse enrichments coincide with episodes of p enrichment thereby implicating a common set of environmental controls on these processes together our dataset implies deposition under a predominantly anoxic water column with periodic fluctuations to more oxidizing conditions because of connections to a large oxic reservoir containing se oxyanions and other rse s as well as sulfate in the open ocean this is broadly consistent with the depositional setting of many modern and recent phosphorites thereby tying these ancient deposits to a common depositional mechanism in light of these data we propose that the broader prevalence of phosphogenesis in the paleoproterozoic era was driven by growth of the seawater oxidant reservoir namely sulfate thus enabling diagenetic apatite precipitation in basins with high rates of export production particularly by facilitating the activity of sulfide oxidizing bacteria this suggests that the muted authigenic p burial observed in marginal marine siliciclastic sedimentary rocks during other intervals of the precambrian was not merely a result of low dissolved p levels in the global deep ocean but also was influenced by sulfate scarcity and strongly reducing bottom water conditions

two brine model of the genesis of strata bound zechstein deposits kupferschiefer type poland these kupferschiefer deposits were probably formed as a result of a mixing of two brines the upper cold brine ucb is an unmineralized brine rich in na ca cl and so4 with a ph 7 and originating from evaporites overlying the metal bearing zechstein rocks the lower hot brine lhb rich in mg k cl so4 and co3 with a ph 7 formed in sediments in the central part of the zechstein basin at a depth of 7 000 m this brine was subjected to heating and upward convection toward the fore sudetic monocline along the bottom of the z1 carbonates during its migration it caused albitization serpentinization and leaching of the primary metal deposits in rocks underlying the zechstein becoming enriched in heavy metals the mineralization process being a result of the mixing of the two brines ucb and lhb and catalytic oxidation of the organic matter of the black shale were initiated at shallow depths in the area of the fore sudetic monocline the boundary of the two brines generally overlapped the strike of the black shale

a multistage origin for kupferschiefer mineralization new re os age determinations on mineralized material from the polish kupferschiefer elucidate the timing of mineralization and thus the likely mechanisms of ore deposition three mineralization parageneses were analysed a chalcocite as pore space filling in sandstone b disseminated cu mo mineralization in shale and c massive bedded copper sulphides the resulting ages fall into two ranges 245 2 1 6 264 7 1 8 ma and 162 3 0 8 184 3 2 2 ma these results substantiate previous age determinations although no upper triassic ages were found in this study some of the younger ages for the mineralization could represent alteration and recrystallization of existing sulphides the results confirm that mineralization took place in several stages from soon after kupferschiefer sediment deposition in the upper permian and for at least 100 m y after until at least the cretaceous the genesis of the mineralization can be explained by the episodic release of hydrothermal fluids from the subsiding adjacent southern permian sedimentary basin although the relative importance of each successive mineralizing event for introducing additional metals is as yet unknown