bismuth selenides from st andreasberg germany an oxidised five element style of mineralisation and its relation to post variscan vein type deposits of central europe carbonate veinlets at roter bar a former underground mine in the polymetallic st andreasberg vein district of the harz mountains germany host selenide minerals that are characterised as bi ag bearing clausthalite pbse tiemannite hgse guanajuatite bi2se3 and a number of selenides of bi zn cu ag and pd an unnamed bi pb ag selenide species with some hg and cu ideally bi4pb3ag2se10 is reported here specular hematite is disseminated within the clausthalite at the marginal zones of which other selenide minerals are located the occurrence of bohdanowiczite agbise2 and umangite cu3se2 constrains the formation temperature to 120 c and the selenide hematite assemblage plus barite in the carbonate gangue identifies highly oxidised conditions selenide assemblages of pb bi ag with and without co and ni occur in many parts of the variscan basement of central europe harz erzgebirge schwarzwald and bohemian massif and represent a high oxidation variety of five element ag as bi co ni veins

limnologic analysis of gusev crater paleolake mars abstract the survey of the hydrogeologic system formed by gusev crater and ma adim vallis aeolis subquadrangle of mars points out evidence for the existence of an ice covered lake in gusev crater a first lake was formed by the drainage of the aquifer in the region surrounding gusev before the entry of ma adim vallis in the crater the existence of a former lake in gusev is deduced from the morphology of the ma adim delta its comparison with terrestrial antarctic analogs argues for the presence of an ice covered lake in gusev at the time that the southern part of the crater s rampart was breached by ma adim first release and for a subice lacustrine construction of the valley s delta our survey shows that ma adim vallis may have entered gusev crater as late as late hesperian early amazonian as part of a second lake episode the relationship between the variation of the gusev lake water level the volume of the lake and the surface of the lake bed is established by our bathymetric model the elevation of the former lake is deduced from the elevation of the mesa like structures in the delta of ma adim vallis furthermore the correlation of the crater frequency of gusev rampart with mars stratigraphic age shows that lakes may have occupied gusev crater over a period of time covering 2 gyrs from the formation of the crater to the last episode of water release from ma adim vallis though it is most likely that the lake was episodical the recurrence of abundant water in gusev crater makes this site a high priority for missions either for martian resource exploration or for the search of life

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

element and isotope geochemical investigations of the kupferschiefer in the vicinity of rote faule indicating copper mineralization sangerhausen basin g d r abstract based upon extensive data on the elemental and isotopic compositions of kupferschiefer of the sangerhausen basin and according to results of trace element and structural investigations of bitumen extracts trends of lateral and vertical distribution of various elements and genetic assertions are presented irregular positions of f v se au and u in the correlation diagram peculiarities of the lateral distribution of these elements abnormally high elemental concentrations in the rocks and in the bituminous extracts as well as alterations discovered in the composition of hydrocarbon groups and their structures support the idea of an influx of oxidizing metalrich waters moving through the rote faule from the rotliegendes basin into the kupferschiefer sediment isotope geochemical investigations carbon nitrogen and oxygen of organic carbonate and silicate fractions were carried out in order to characterize more precisely the conditions of sedimentation and the regime of diagenesis the contrary 13 c curves of pb zn facies and rote faule facies and the 13 c enrichment in the organic matter of rote faule can be explained by different redox conditions during sedimentation and or diagenesis furthermore the decreasing 18 o values of carbonates of the rote faule also suggest an influx of meteoric waters the results oppose a final syngenetic to early diagenetic fixation of the metal contents in kupferschiefer areas in the vicinity of rote faule the established model of influx of metalliferous fluids which arose from the rotliegendes is of local interest for element input and element redistribution

reconciling late ordovician 440 ma glaciation with very high 14x co2 levels geochemical data and models suggest a positive correlation between carbon dioxide changes and climate during the last 540 m y the most dramatic exception to this correlation involves the late ordovician 440 ma glaciation which occurred at a time when co2 levels may have been much greater than present 14 16x since decreased solar luminosity at that time only partially offset increased radiative forcing from co2 some other factor needs to be considered to explain the glaciation prior work with energy balance models ebms suggested that the unique geographic configuration of gondwanaland at that time may have resulted in a small area of parameter space permitting permanent snow cover and higher co2 levels however the crude snow and sea ice parameterizations in the ebm left these conclusions open to further scrutiny herein we present results from four experiments with the genesis general circulation model with co2 levels 14x greater than present solar luminosity reduced 4 5 and an orbital configuration set for minimum summer insolation receipt we examined the effects of different combinations of ocean heat transport and topography on high latitude snow cover on gondwanaland for the no elevation simulations we failed to simulate permanent summer snow cover however for the slightly elevated topography cases 300 500 m permanent summer snow cover occurs where geological data indicate the ordovician ice sheet was present these results support the hypothesis based on ebm studies further results indicate that although average runoff per grid point increases substantially for the ordovician runs the decreased land area results in global runoff 10 30 less than present with largest runoff reductions for flat topography this response has implications for co2 runoff weathering parameterizations in geochemical models finally simulated tropical sea surface temperatures ssts are the same or only marginally warmer than present this result is consistent with evidence from other warm time intervals indicating small changes in tropical ssts during time of high co2

permian to early triassic magnetostratigraphy from the central european basin in poland implications on regional and worldwide correlations abstract permian early triassic rocks sampled in 15 outcrops 93 hand samples and 11 unoriented boreholes 630 hand samples from the polish part of the central european basin were studied paleomagnetically in spite of extensive remagnetization affecting 50 of samples from the boreholes a magnetic polarity sequence was compiled the polarity pattern is not only common for many sections from the investigated area but also convergent with the global synthetic magnetostratigraphic scale the lower rotliegend early permian rocks contain a reversed polarity record while the upper rotliegend late permian early triassic sediments are characterized by mixed polarity magnetization within the buntsandstein part of that mixed megazone 14 magnetic zones were found buntsandstein sedimentation started with a normal polarity zone which may be compared with that of early griesbachian defined in several places in the world the polarity record noted in the middle buntsandstein sediments could indicate significant stratigraphic gaps or condensations near the middle buntsandstein and rot boundary the comparison of the upper buntsandstein polarity with the early middle triassic magnetostratigraphic data from other basins suggests that the majority or even all the rot sediments should be included in the anisian

re os age of non mineralized black shale from the kupferschiefer poland and implications for metal enrichment six samples of non mineralized black shale from a kupferschiefer section in the northern part of the polish zechstein basin zdrada ig 8 drill hole 1026 16 1026 90 m were studied for re os isotopes and selected major and trace elements these black shales averaging 5 82 wt corg and 1 69 wt stot display very low base metal values up to 106 ppb cu 792 ppb pb and 144 ppb zn and have abundances of 64 1376 ppb re and 0 37 1 25 ppb os with a 187os 188os ratio of 6 95 22 5 the regression of all re os data yields an age of 247 20 ma which is within the range of uncertainties of previous rb sr and k ar geochronological studies the scatter in the re os data can be explained in terms of fluctuations in sedimentary conditions i e restricted basin with terrestrial influence

the magnetization of clay rich rocks in sedimentary basins low temperature experimental formation of magnetic carriers in natural samples abstract rocks are often magnetically altered during burial thus providing a useful method to study their thermo chemical history in order to improve the understanding of burial diagenetic magnetization we experimentally synthesized magnetite in natural samples lower jurassic argillites from the paris basin were heated to 150 c under a confined atmosphere of argon when a magnetic field was applied during the heating a chemical remanent magnetization was acquired rock magnetism studies reveal that most of the newly formed magnetic carriers were magnetite using anhysteretic remanent magnetization as a measure of the quantity of magnetite an increase of up to 150 after heating was observed ferrimagnetic iron sulphide and hematite are observed to have formed in samples composed of less than 3 calcite and new magnetite is sometimes completely absent in samples containing less than 0 5 calcite hysteresis measurements suggest that the new magnetite is in the pseudo single domain state scanning electron microscope studies indicate that the new magnetic carriers are associated with pre existing pyrite the magnetic transformations during the experiments involved a fluid which reacted with iron bearing and sulfur bearing minerals in ways depending on local redox conditions this study shows that magnetite can be produced in argillaceous sediments at the normal temperatures and pressures found in sedimentary basins without any external supply from long range fluid flow

the role of the kupferschiefer in the formation of hydrothermal base metal mineralization in the spessart ore district germany insight from detailed sulfur isotope studies the spessart district sw germany located at the southwestern margin of the permian kupferschiefer basin in central europe hosts abundant stratabound and structurally controlled base metal mineralization the mineralization styles identified are 1 stratabound cu pb zn ag ores in zechstein sedimentary rocks 2 structurally controlled cu as ag ores in zechstein sedimentary rocks 3 crosscutting co ni bi as and cu fe as veins 4 stratabound metasomatic fe mn carbonate ores in zechstein dolomite 5 barren barite veins and 6 fe mn as veins in permian rhyolites building on previous work that involved mineralogical textural and chemical characterization of the major mineralization types we have performed a comprehensive sulfur isotope study that applied both conventional and novel laser ablation multi collector inductively coupled plasma mass spectrometry techniques the 34s values of sulfide minerals from the different ore types are consistently negative and highly variable in the range between 44 5 and 3 9 whereas the 34s values of barite are all positive in the range between 4 7 and 18 9 remarkably stratabound and structurally controlled mineralization in zechstein sedimentary rocks has the least negative 34s values whereas vein type deposits have consistently more negative 34s values the observed pattern of sulfide 34s values can be best interpreted in terms of fluid mixing at the basement cover interface hydrothermal fluids originating from the crystalline basement migrated upward along subvertical fault zones and were periodically injected into groundwaters that were flowing in the post variscan sedimentary cover these groundwaters had interacted with the zechstein sedimentary rocks resulting in fluids characterized by elevated concentrations of reduced sulfur with negative 34s values and alkaline ph repeated mixing between both chemically contrasting fluids caused rapid and efficient precipitation of sulfide ore minerals in hydrothermal veins with highly variable but distinctly negative 34s values

antarctic paleolake sediments and the search for extinct life on mars evidence of lakes in mars history is substantial the proposed similarities between the ancient martian environment and certain modern environments on earth have led exobiologists to study antarctic lakes as analogs to those purported to have existed on mars we have investigated modern sedimentation processes especially with respect to 13c of carbonate and organic matter in lakes in the mcmurdo dry valleys region of east antarctica and assessed various paleolake deposits with respect to their utility as martian analogs and targets for future mars exobiology missions three main types of paleolake deposit were identified and assessed strand lines perched deltas and lacustrine sand mounds deltas are usually identified as good targets but our research shows that authigenic carbonates are not readily identifiable in the sediments large deltas although most likely to attract attention through remote sensing generally are difficult sites for discovery of paleobiological matter and 13c signals follow no coherent pattern lacustrine sand mounds on the other hand contain abundant authigenic carbonate and freeze dried organic matter and appear to be excellent records of paleolimnological conditions the advantage of studying lake bottom deposits versus lake edge deposits is retrieval of a stable lake wide signal deltas are therefore most useful in that they are generally large scale features capable of drawing attention to a region of potential for the discovery of smaller lacustrine sand mounds

the southern rhine graben a new view of the initial phase one of the puzzling features of the southern end of the rhine graben is the dinkelberg tabular jura block on the eastern shoulder of the graben it is dissected by a large number of faults the most notable ones forming a field of narrow little grabens and half grabens whose bordering faults converge at the level of the middle triassic evaporites which points to decollement at that horizon the little grabens were traditionally considered to be of oligocene age coeval with the main taphrogenesis of the rhine graben two hypotheses were offered for their formation one ascribing them to extension on the extrados of large basement folds the other to gravity sliding on paleoslopes recent field work uncovered overwhelming evidence for an eocene age of the little grabens the time of the initial phase of rhine graben formation at that time there were neither large basement folds nor paleoslopes of any significance and therefore the two hypotheses offered until now do not work however the map view pattern of the field of faults offers a somewhat unusual way out of the dilemma this pattern is most prominently displayed in the dinkelberg area north of the rhine there a lane of narrow decollement grabens with a mean nne strike is confined within the nw striking dinkelberg graben which is much wider and rooted in the basement it is also very shallow with a subsidence on the order of 100 m the lane of decollement grabens forms a dextral en echelon pattern with respect to the dinkelberg graben suggesting stretching of the post evaporite sequence above a basement essentially extended by strike slip this model though not as clearly expressed is also compatible with the data in the rest of the dinkelberg tabular jura block it also fits surprisingly well a theoretical model by withjack and scheiner 1982 that predicts a dominance of strike slip in the marginal area of a system consisting of extension superimposed on doming

thermophiles early biosphere evolution and the origin of life on earth implications for the exobiological exploration of mars mars holds great interest for exobiology and presently stands center stage in our plans to explore the inner solar system for signs of past or present life with the spectacular success of the pathfinder mission golombek 1997 and upcoming mapping efforts by the mars global surveyor orbiter albee et al 1998 it is an especially appropriate time to revisit some important issues in mars exobiology the papers making up this journal of geophysical research planets special issue on mars were the outgrowth of an american geophysical union special session entitled exploring for a martian biosphere which was presented at the fall meeting in san francisco in 1995 farmer 1995a together these papers provide a context for evaluating some fundamental issues in the exobiological exploration of mars topics covered fall into the following broad categories 1 environments and conditions required for the origin of life hydrothermal environments as sites for prebiotic chemical synthesis shock and schulte this issue 2 early martian environments as a context for the evolution and diversification of life on mars early impact hazards sleep and zahnle this issue early volatile and climate history of mars haberle this issue and ice covered lakes as habitats for early life doran et al this issue 3 exploring for extant martian life results of the viking missions klein this issue environmental extremes for martian life clark this issue and planetary protection and mars sample return devincenzi et al this issue and 4 exploration strategies phosphate minerals as targets for chemofossils mojzsis and arrhenius this issue and the role of robotic surface missions stoker this issue

does crater saturation equilibrium occur in the solar system abstract similarity is found in crater densities on the most heavily cratered surfaces throughout the solar system this is hypothesized to result from a steady state saturation equilibrium being approached or achieved by cratering processes this hypothesis conflicts with some recent interpretations however it accounts for 1 a similarity in maximum relative crater density below certain theoretically predicted values on all heavily cratered surfaces 2 a leveling off at this same relative density among 100 m scale secondary craters in populations on lunar maria and other sparsely cratered lunar surfaces 3 the approximate uniformity of maximum relative densities on saturn satellites in spite of dramatic variations predicted from nonsaturation models assuming heliocentric impactors the lunar frontside upland crater population sometimes described as a well preserved production function useful for interpreting other planetary surfaces is found not to be a production function it was modified by intercrater plains formed at least partly by early upland basaltic lava flooding recently confirmed spectrophotometrically consistent with this counts in pure uplands those lacking intercrater plains match the proposed saturation equilibrium density variations among large d 64 km crater populations are found but these may involve several hypothesized mechanisms that rapidly obliterate large craters especially on icy surfaces recent models in which different populations of interplanetary bodies hit different planets need further appraisal

reos and s isotopic constraints on the origins of two mineralization events at the tangdan sedimentary rock hosted stratiform cu deposit sw china abstract the tangdan stratiform cu deposit in the kangdian region of south china is hosted in sedimentary rocks of the late paleoproterozoic to early mesoproterozoic dongchuan group orebodies mainly occur in dolostone and black shale above a thick sequence of hematitic sandstone and siltstone mineralization consists mainly of bedding parallel stratiform ores with minor amounts of discordant vein type ores both stratiform and vein type ores are composed of bornite and chalcopyrite with minor chalcocite and digenite associated with gangue minerals including ankerite dolomite calcite and quartz cu sulfides from vein type ores contain 122 293 ppb re much higher than those of stratiform ores 0 6 14 ppb re they have highly radiogenic os with re os model ages ranging from 1413 to 1457 ma and a weighted mean re os model age of 1432 19 ma 2 mswd 0 30 which is within uncertainty in agreement with isochron ages of 1401 30 ma 2 mswd 0 67 and 1397 71 ma 2 mswd 0 22 using 187 re 188 os versus 187 os 188 os and 187 re versus 187 os regression respectively in contrast sulfides from stratiform ores did not yield meaningful model ages due to the extremely low concentrations of re and radiogenic os however early studies have shown that the stratiform ores were likely formed at 1700 ma during the diagenesis of the host strata sulfides from the vein type ores have 34 s values ranging from 15 to 8 significantly lower than those of stratiform ores 3 to 10 suggesting that organic matter may have been involved in the formation of the vein type ores contrasting re os and s isotopes suggest that the two types of ores at the tangdan deposit were likely formed from different ore forming fluids we propose that stratiform ores were precipitated from basinal fluids during the early evolution of the rift basin whereas the vein type ores were formed due to a much younger thermal event during which hydrothermal fluids interacted with overlying black shale to account for the high re and negative 34 s values this study demonstrates that re os isotopes of sulfides can be used to study the origin of hydrothermal system

duration of the ma adim vallis gusev crater hydrogeologic system mars abstract ma adim vallis and gusev crater aeolis subquadrangle of mars formed a complex hydrogeologic system through time crater statistics over five geologic units coupled with morphologic and geologic observations show that this system was active over a period ranging from 0 7 to about 2 billion years these results make the floor of gusev crater one of the most prominent martian depositional features the last aqueous sedimentary deposition could have occurred during early amazonian

a case for ancient evaporite basins on mars observations indicate that a martian analog to the earth s salt pans and saline lakes of arid regions may have existed in crater basins during mars early noachian epoch terraced and channelized crater basins point to ponding of surface water as well as possible prolonged and evolving base levels in addition supportive evaporite basin analogs are offered for three other morphologic features of martian crater basins an evaporite basin model for crater basins on mars has major implications for the mechanical chemical and even biological processes that potentially have operated in mars past and represent a spectrum of potential mineral resources

7 4 kupferschiefer copper deposits of sw poland lubin sieroszowice district lat 51 35 n long 16 6 e

clay mineralogy crystallinity and k ar ages of illites within the polish zechstein basin implications for the age of kupferschiefer mineralization a discussion sir bechtel et al 1999 suggest that the formation of diagenetic illite in the kupferschiefer of the polish zechstein basin was coeval with the mineralizing event the ages estimated for the diagenetic illites are in the range of 190 to 216 ma a middle to late triassic date 240 220 ma for the high grade mineralization in the kupferschiefer was inferred from the remanent magnetization of hematite inside the rote faule zone in southwestern poland and the polar wander paths of europe and russia jowett et al 1987 in conclusions p 271 bechtel et al 1999 stated within limits of error the ages inferred for the diagenetic illites inside the mining district of the polish kupferschiefer 190 216 ma are in agreement with the date of the kupferschiefer mineralization proposed by jowett et al 1987 from paleomagnetic measurements thus paleomagnetic data were used for verification of indirect age determination of the main mineralizing event according to bechtel et

genesis of kupferschiefer cu ag deposits by convective flow of rotliegendes brines during triassic rifting extensive and rich cu ag sulfide mineralization occurs in poland across the contact between the upper permian zechstein restricted marine sequence and the lower permian rotliegende continental volcanic and clastic sequence geologic evidence suggests that the mineralization was formed during late diagenesis when metalliferous brines migrated through the rotliegende leaching metals from the volcanic detritus and up the flanks of basement highs possibly along fracture porosity to the pyritic kupferschiefer and zechstein limestone above thick evaporites in the lower zechstein preclude a vertical flow through model but metal zoning attitudes suggest that the brines overturned where the rotliegende pinched out against the highs and moved laterally along the base of the zechstein toward the basin centers presumably to sink back down into the rotliegende completing a convection cell a middle triassic paleomagnetic age for the metal zoning and kimmerian attitudes of dilatant sulfide veinlets indicate that the mineralizing event coincided with continental rifting associated with the opening of the tethys ocean slow unicellular convection may be commonplace in sandstone basins where small lateral temperature gradients delta t exist but greater velocities are necessary to form large orebodies an anomalous tensional and thermal event such as rifting can increase velocities by increasing permeability slope angle or delta t the paleothermal structure of southwestern poland was determined by modeling the conductive heat flow in 14 one dimensional geologic sections which described the evolution of the basin architecture for 10 m y in the early triassic rifting was simulated by increasing the lower boundary condition from 500 degrees to 1 000 degrees c at 25 km this thermal pulse produced a surprisingly high delta t of 25 degrees c across the lubin ore district solely from differences in thermal conductivities between the basement high 4 2 w m degrees c the sandstone 2 5 w m degrees c and the shale basin center 1 25 w m degrees c unicellular convection patterns would be induced by the lateral boundary conditions of warm basement highs and cold shale centers and by the greater horizontal permeability these cells were 15 to 20 km long 400 m high and subhorizontal a slope angle of 2 degrees and a permeability of 1 d produces a convection velocity of 13 cm yr which with a copper solubility of 1 000 mg kg in 20 to 30 percent ca na cl brines in equilibrium with hematite can form the lubin deposit in less than 6 m y using a fracture permeability of 2 d and a solubility of 300 mg kg the time needed is less than 10 m y the konrad mine can be formed in similar time periods without the continuous recycling of the brine inherent in convective flow 20 times or more the metal solubilities needed to form the lubin deposits by a flow through model would be unreasonably high natural gases likely migrated along with the metalliferous brines and helped convection by creating secondary porosity and increasing the buoyancy of the fluids because the fluids are recirculated and not expelled convection provides a way in which secondary migration of methane and petroleum can occur effectively in solution as well as in separate phases

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

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

early cretaceous mineralizing activity in the st andreasberg ore district southwest harz federal republic of germany in the st andreasberg ore district southwest harz at some time between the main and subsequent stages of mineralization sensu wilke 1952 potassium feldspar adularia was formed hydrothermally based on isotopic dating rb sr 40ar 39ar the formation of this mineral is ascribed to the early cretaceous thus part of the st andreasberg mineralization is proved to have been formed in the late mesozoic the mineralization process forming feldspar does not coincide with magmatic phases of the area

the composition of brines in the early diagenetic mineralization of the permian kupferschiefer in germany the kupferschiefer is an approximately 0 5 m thick black marly shale of lower zechstein age in germany if one includes some of its footwall and hanging wall it contains 300 mt cu 800 mt zn and 300 mt pb the regional pattern of metal distribution demonstrates its relationship to variscan and permian tectonic structures faults and the topographic relief of the basement apparently controlled the uprise and lateral migration of reducing and slightly acid hot brines from deeper crustal levels to supply the metals for the mineralization of the proto kupferschiefer deep fluids are mainly richer in zn than pb and richer in pb than cu mixing of such slightly acid fluids with slightly alkaline formation waters seawater caused a gradient in ph from about three to eight and in sulfide concentration most of the sulfide came from dissolved pyrite which was very light in sulfur isotopes this gradient controlled the sequential precipitation of bornite chalcopyrite chalcocite galena and sphalerite which is observed in a lateral and vertical zoning of these sulfides the fluids experienced a fractionation of the metals during migration over meter to kilometer distances from the tectonically controlled vents within the unconsolidated proto kupferschiefer close to the vents the sulfide deposits attained concentrations up to 2 zn pb cu the migration of the metals over large distances took place in unconsolidated sediment thus the major mineralization of the kupferschiefer has to be classed as an early diagenetic process

recent aqueous environments in martian impact craters an astrobiological perspective the discovery of gullies and debris aprons raises the question of the existence of aqueous environments on mars in recent geological times and its astrobiological implications three cases of such environments are surveyed at moc high resolution in the e gorgonum chaos and newton and hale craters the regional setting of these craters suggests that the mechanisms of aquifer destabilization flow discharge and gully formation in these three cases result from local geological triggers that can include impact cratering and tectonic processes rather than climate or insolation factor we take as a working hypothesis that microbial life appeared on mars in ancient geological times probably in a geothermal environment but potentially evolving via infrared detection systems to give photosynthetic communities under the selective pressure of energetic solar radiation we hypothesize that some microbial communities could have survived underground in either dormant or active state or that their biomolecules could be preserved either frozen or desiccated in the subsurface beneath the upper oxidized zone we assess the known environmental constraints for life and what type of potential habitats are provided in these three craters by aquifer discharges using comparison with terrestrial analogues and their associated microbial communities these environments include 1 the release of water on a dry crater floor in e gorgonum and the possibility for microorganisms and preserved biomolecules to be flushed out and mixed in with the sediment exposed at the surface 2 the evidence of a recent lacustrine episode in the newton crater with analogy to antarctic dry valley lakes 3 the exposure on the floor of hale crater of material from a regional subsurface that is likely to have retained traces of one of the oldest martian bodies of water recognized to date parker et al 2000 in the argyre basin we show how the water in argyre 3 8 billion years ago gya was likely to have been alterated by hydrothermal processes and how the subsequent formation of the 150 km hale crater on the northern ring of argyre generated hydrothermal pumping this accounts for the anomalously high location of the springs on the crater crests today with respect to the rest of the regional subsurface distribution finally we envision current impact cratering as a factor for destabilizing aquifers on mars today thus creating new environments we analyze the implications of impacts for two geological types of rock units that could harbor traces of life as a result we compare the potential of astrobiological exploration of crater floors rims and ejecta on future missions to mars

the role of organically bound sulphur in stratiform ore sulphide deposits abstract low and high molecular weight organic sulphur compounds were analyzed in a selected number of samples of the permian kupferschiefer poland their significant presence in these mature samples supports the hypothesis that during deposition and shortly thereafter labile organic sulphur compounds must have been very abundant this assumption has led to a new model for metal accumulation based on a slow and gradual release of sulphur from these labile organic sulphur compounds during increasing diagenesis

provenance of cretaceous clastics in the subhercynian basin constraints to exhumation of the harz mountains and timing of inversion tectonics in central europe the harz mountains and the adjacent subhercynian cretaceous basin figure as the most prominent surface representative for late cretaceous inversion structures in central europe facies depositional architecture and provenance of the basin fill reflect mechanisms and timing of the exhumation of the harz from hauterivian to early santonian there is no evidence for detrital input from the nearby harz area sediments are mature quartzarenites derived from paleozoic basement rocks and or recycled permian to mesozoic sedimentary rocks this situation changed drastically in middle to late santonian when freshly exhumed and eroded mesozoic sedimentary cover rocks of the harz were delivered into the basin feldspar and lithoclasts reflect erosion of triassic and in places jurassic to turonian strata apatite and garnet in heavy mineral spectra are derived from largely unweathered lower triassic buntsandstein as indicated by apatite and garnet chemistry in early campanian paleozoic lithoclasts indicate erosion cutting down into the basement of the harz simultaneous strong decrease of feldspar garnet and apatite suggest an almost complete removal of the 2 3 km thick mesozoic cover of the harz within only 2 4 myr this translates into an exhumation rate of approximately 1 mm a consistent with apatite fission track data from granitoid rocks of the harz mountains

late paleoproterozoic to early mesoproterozoic tangdan sedimentary rock hosted strata bound copper deposit yunnan province southwest china sedimentary rock hosted strata bound copper deposits are widespread in the kangdian region of the central yunnan and southern sichuan provinces southwest china the deposits occur within weakly metamorphosed rocks of the late paleoproterozoic to early mesoproterozoic dongchuan group and are spatially associated with discordant breccia bodies that are interpreted as having formed from salt diapirs the tangdan deposit the largest in the region consists of stratiform and discordant orebodies predominantly hosted in dolostones immediately above hematitic sandstones and siltstones and in black shales above the dolostones host rocks for the deposit display a complex paragenetic sequence of alteration and mineralization early sodic alteration resulted in the growth of both albite and ferroan dolomite later potassic alteration resulted in the precipitation of potassium feldspar and locally biotite in argillaceous layers sulfide mineralization was temporally and spatially associated with silicification that postdated both sodic and potassic alteration textures suggest that silicification may have preferentially affected evaporite minerals in the dolostones copper sulfides form bedding parallel disseminations veinlets and to a lesser extent stockworks copper sulfides are dominated by chalcopyrite with lesser bornite and chalcocite hypogene chalcopyrite and bornite from the tangdan deposit have 34s values that range from 12 7 to 9 3 and cluster between 3 to 5 the values suggest derivation from mesoproterozoic marine sulfates the dolostone host rocks have relatively homogeneous c and o isotope values ranging from 0 2 to 1 3 13cv pdb and from 19 1 to 22 4 18ov snow carbonate minerals in quartz sulfide veins display both a trend toward lighter oxygen isotope values and a trend to significantly lighter carbon isotope values the light carbon isotope values suggest involvement of organic carbon in the mineralizing process alteration and mineralization at tangdan probably occurred via interaction of oxidized saline brines derived from the underlying red bed sequence with partially to wholly lithified dolostones sulfide precipitation was likely due to both redox reactions and mineralizing fluid ph changes resulting from dolomite and sulfate dissolution the styles of alteration and mineralization at the tangdan deposit are similar to those observed in the central african copperbelt particularly the dolostone hosted orebodies in the mines series of the democratic republic of congo

the thermal stability of near surface ground ice on mars the existence of subsurface water ice on mars has been predicted in several theoretical studies1 5 but there are no definitive observations of its present distribution geomorphic features on the surface of mars have been widely interpreted as evidence for the presence of ground ice6 12 but many of these features are found at near equatorial latitudes where thermal models have predicted that near surface water ice should not be stable under present climate conditions3 13 14 here i present the results of thermal calculations which show that observed geographic variations in the thermal and reflectance properties of martian soils significantly affect subsurface temperatures my results indicate that in certain regions ground ice deposits could exist much closer to the surface and much closer to the equator than previously thought in the future these deposits could be a valuable resource for human exploration15

the kupferschiefer cu ag ore deposits in poland a re appraisal of the evidence of their origin and presentation of a new genetic model the kupferschiefer stratiform copper deposits in central europe have long been considered a classic example of syngenetic mineralization however metal zoning and host rock relationships determined during exploration around the recently discovered lubin district orebodies in southwest poland suggest that the ore may instead be late diagenetic the mineralization occurs as thin extensive blankets of sulphides in the pyritic organic rich basal units of the late permian zechstein restricted marine sequence and in the eolian weissliegendes sandstone at the top of the early permian rotliegendes continental rift sequence of bimodal volcanic rocks and redbeds it is directly underlain and controlled by irregular oval zones of rote faule rf a barren oxidized and reddened portion of the normally dark grey pyritic basal zechstein rocks in plan view the metals occur as successive belts enriched in copper silver lead and zinc which developed laterally from and encircle the rf zones the ore transgres

clausthalite pbse and tiemannite hgse from the type locality new observations and implications for metallogenesis in the harz mountains germany abstract clausthalite and tiemannite from the type locality clausthal in the harz mountains germany have virtually gone undocumented since their discovery in the nineteenth century the minerals and their selenide assemblages are here documented in historical samples from the konigin charlotte mine in the former clausthal pb zn ag mining district clausthalite and tiemannite are the main selenide components naumannite is generally subordinate whereas klockmannite and eskebornite are accessory minerals the absence of inversion lamellae in naumannite constrains the formation temperature to 87 sr 86 sr values of 0 70914 and 0 71133 for two samples of tiemannite aggregates containing celestine anhydrite inclusions the clausthal selenide assemblages postdated the main sulfide bearing polymetallic vein style mineralisation of the harz mountains

origin and evolution of valleys on martian volcanoes morphological analyses of six martian volcanoes ceraunius tholus hecates tholus alba patera hadriaca patera apollinaris patera and tyrrhena patera indicate that fluvial processes were the dominant influence in the initiation and subsequent development of many dissecting valleys lava processes and possibly volcanic density flows were also important as valley forming processes fluvial valleys are especially well developed on alba patera ceraunius tholus and hecates tholus these valleys are inset into the surrounding landscape they formed in regions of subdued lava flow morphology contain tributaries and tend to widen slightly in the downstream direction lava channels on alba patera are located on the crest of lava flows and have a discontinuous irregular surface morphology and distributary patterns these channels sometimes narrow toward their termini possible volcanic density flow channels are located on the northern flank of ceraunius tholus valleys dissecting apollinaris patera hadriaca patera and tyrrhena patera appear to have a complex evolution probably a mixed fluvial and lava origin they are inset into a subdued possibly mantled surface lack tributaries and either have fairly constant widths or widen slightly downvalley valleys surrounding the caldera of apollinaris appear to have formed by fluvial and possibly by volcanic density flow processes while those on the apollinaris fan structure may have a mixed lava and fluvial origin valleys on tyrrhena have broad flat floors and theater heads which have been extensively enlarged probably by sapping hadriaca valleys have a trough shaped form like those on the fan structure on apollinaris but are more enlarged and have theater heads fluvial valleys on the martian volcanoes generally followed a two stage evolutionary sequence similar to that of the hawaiian volcano valleys including 1 initial formation by surface runoff and 2 subsequent enlargement by groundwater sapping because basalt is highly permeable valleys on hawaii island formed only in regions where lava flows were mantled by less permeable volcanic ash similarly fluvial valleys on the martian volcanoes particularly those on alba patera formed in regions where lava flow morphology is subdued probably by ash mantling thus the presence or absence of this mantling may explain why fluvial valleys are present on some martian volcanoes but not on others of the same age the formation of fluvial or fluvial modified valleys on the older volcanoes ceraunius hecates tyrrhena apollinaris and hadriaca implies that surface and near surface water activity was widespread during late noachian to early hesperian period of heavy bombardment however the presence of anomalously young fluvial valleys on alba patera indicates that fluvial valley activity did not entirely cease near the end of late heavy bombardment but rather persisted in isolated regions until mid to late amazonian

a mid triassic paleomagnetic age of the kupferschiefer mineralization in poland based on a revised apparent polar wander path for europe and russia extensive mineralization occurs in southwest poland as zoned blankets of cu ag pb zn sulphides in the kupferschiefer and zechstein limestone across the base of the late permian zechstein restricted marine sequence and in the weissliegendes sandstone at the top of the early permian rotliegendes continental volcanic and siliciclastic sequence the rote faule rf zone an oxidized hematitic equivalent of the normally pyritic basal zechstein directly underlies the copper ore and is part of the metal zoning although the origin has generally been considered to be syngenetic geologic controls of the rf ore systems in poland suggest a late diagenetic origin by converting metalliferous brines migrating through the rotliegendes clastic redbeds up along basement highs oxidizing the pyritic kupferschiefer to form the rf and precipitating base and precious metals on the reduced side of this oxidation reduction front a paleomagnetic study of the ore zone in five mines in poland the rf zone in three mines and of the barren pyritic basal zechstein from outcrops and quarries in poland germany and england was undertaken to determine the absolute age of the mineralization in the barren pyritic rocks and the copper sulphide ore thermal demagnetization and vector subtraction revealed an unstable low temperature first remanence component 76 9 n 12 2 e a63 1 6 parallel to the ambient field and a second higher temperature component 82 6 n 145 9 e a63 1 9 which could be miocene 10 20 ma or less likely cretaceous 110 ma or jurassic 180 ma this second component is erased at 350 400 c and is thought to be carried by a product of weathering after alpine age uplift and erosion no primary magnetization could be isolated in the copper or pyritic zones the rf hematite however contained a very stable third reversed component 49 0 n 157 2 e a63 2 2 which was revealed typically between 500 and 620 c and is considered to represent a secondary chemical remanent magnetization acquired during the mineralizing process in order to date the isolated magnetic components carboniferous to neogene apparent polar wander apw paths for europe and russia were constructed using paleopole catalogs mean paleopoles every 10 ma from 350 to 0 ma with a63 circles of confidence were calculated as running averages using overlapping 20 and 30 ma time intervals the rf pole corresponding to the third remanence component coincides extremely well with a middle triassic age of 240 ma on the 20 ma apw path and a late triassic age of 230 ma on the 30 ma apw path statistical analysis yields upper and lower age limits of 250 and 220 ma this triassic paleomagnetic age supports the proposed late diagenetic origin of the kupferschiefer ore deposits and suggests that the rf ore systems were formed immediately after triassic continental rifting associated with the opening of the tethys ocean to the south a likely source of the thermal anomaly necessary to initiate adequate convective velocities within the rotliegendes clastic basins

surviving the limits to life at the surface of mars the harshness of the environment at its surface severely limits the survival of unprotected terrestrial organisms on mars however the martian geologic record is consistent with an earlier history with much different climatic conditions more conducive to life followed by an extended climate change which led to the currently inhospitable state such a transition is ideal for evolutionary adaptation to new conditions because it provides both the forcing function and the extensive time for progressive specializations it is shown that against each of the current limits to life organics deprivation restricted amounts and physical forms of h2o limited availability of other key nutrients ionizing radiation insult and strongly oxidizing chemical species there are plausible countermeasure solutions most but not all of these mechanisms already exist as known examples in terrestrial biota a combination of these adaptations could conceivably allow highly tailored organisms either active or dormant to survive at or very near the surface of mars even in carefully preserved regolith samples returned to earth microorganisms could be difficult to detect without specific biochemical probes and or purposeful biological amplification by selective enhancement of the supply of nutrients optimized incubation parameters and highly sensitive detection of metabolic activity

impact crater lakes on mars the robotic search for life on mars centers on identifying accessible environments where the biological catalyst water has existed the formation of large impact craters on mars 65 km diameter may have resulted in the creation of ice covered impact crater lakes which would not freeze for thousands of years even under present climatic conditions water could be supplied from deep confined aquifers penetrated by the impact craters without the need for surface melt water freezing of the lakes is postponed owing to heat from impact generated melt bearing deposits from impact related uplift of hotter rocks from depth and from the latent heat of freezing of a deep crater lake abundant morphologic evidence for ancient crater lakes has not been found in viking images except for craters associated with outflow channels however ice covered crater lakes could have formed and further searches for evidence of these lakes are warranted the lake deposits from dissected impact craters may represent one of the best targets for future surface exobiology investigations or sample return missions from mars

global time scale and regional stratigraphic reference scales of central and west europe east europe tethys south china and north america as used in the devonian carboniferous permian correlation chart 2003 dcp 2003 the boundaries of the devonian carboniferous and permian stages of the global stratigraphic reference scale abbreviated to global stratigraphic scale gss are described in relation to the biostratigraphic and or lithostratigraphic units of the regional stratigraphic reference scales abbreviated to regional stratigraphic scales rss of central and west europe east europe tethys south china eastern tethys and north america in their type regions the boundaries of gss units rarely coincide with those of homonymous rss units moreover the definitions of some rss units have changed several times over the last decades and subsequent misunderstanding of the stratigraphical significance of these changes has often introduced errors into proposed global correlation charts the stratigraphic framework proposed in our global devonian carboniferous permian correlation chart 2003 dcp 2003 devonian carboniferous permian correlation chart 2003 menning m schneider j w alekseev a s amon e o becker g von bitter p h boardman d r bogoslovskaya m braun a brocke r chernykh v chuvashov b i clayton g dusar m davydov v i dybova jachowicz s forke h c gibling m gilmour e h goretzki j grunt t a hance l heckel p h izokh n g jansen u jin y g jones p kading k ch kerp h kiersnowski h klets a klug ch korn d kossovaya o kotlyar g v kozur h w laveine j p martens th nemyrovska t l nigmadganov a l paech h j peryt t m rohn r roscher m rubidge b schiappa t a schindler e skompski s ueno k utting j vdovenko m v villa e voigt s wahlman g p wardlaw b r warrington g weddige k werneburg r weyer d wilde v winkler prins c f work d m 2004 abschlusskolloquium dfg schwerpunktprogramm 1054 evolution des systems erde wahrend des jungeren palaozoikums im spiegel der sedimentgeochemie abstracts univ erlangen germany 2004 p 43 herein abbreviated to dcp 2003 and cited as dcp 2003 in references is an attempt to reduce these errors the dcp 2003 is the stratigraphic base for project 1054 of the deutsche forschungsgemeinschaft dfg the evolution of the late palaeozoic in the light of sedimentary geochemistry this composite time scale has been carefully balanced as far as data allows to remove unnecessary artificial compression and expansion of time intervals biozonations and depositional events the ages selected in dcp 2003 are markedly different to those in the geologic time scale 1989 gts 1989 harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge pp 1 263 and in gradstein and ogg gradstein f m ogg j 1996 a phanerozoic time scale episodes 19 1 2 3 4 insert whereas they are closer to those of the geologic time scale 2004 gts 2004 gradstein f m ogg j g smith a g 2004 a geologic time scale 2004 cambridge univ press cambridge pp 1 589 mostly the ages are rounded to the nearest 0 5 ma in order to avoid estimates of questionable accuracy whereas ages of 0 1 ma in the gts 2004 and their error bars of 0 4 ma to 2 8 ma for the devonian to permian stage boundaries suggest an improved accuracy in contrast in the dcp 2003 questionable ages and positions of stratigraphic boundaries are marked by arrows c 2006 elsevier b v all rights reserved

the chemical composition of specular hematite from tilkerode harz germany implications for the genesis of hydrothermal hematite and comparison with the quadrilatero ferrifero of minas gerais brazil the black shale hosted selenide vein type deposit at tilkerode eastern harz germany has specular hematite enclosed in clausthalite pbse the specular hematite has ti and v in amounts of up to 1 wt tio2 and 3 wt v2o5 and subordinate but important contents of mo 22 372 ppm and b up to 68 ppm the tilkerode hematite serves as a reference for hydrothermal hematite formed at relatively low temperatures 150 c the composition of the tilkerode hematite is compared with that of two generations of specular hematite from itabirite hosted iron ore deposits in the quadrilatero ferrifero of minas gerais brazil the first generation of specular hematite represents an early tectonic hematitisation of dolomitic itabirite at aguas claras and occurs as fine grained crystals reconnaissance data indicate that the aguas claras hematite is poorer in ti and v relative to the tilkerode hematite but has 5 10 ppm b and 7 11 ppm li the second generation of specular hematite defines the pervasive tectonic foliation of the gongo soco iron ore this hematite has ti contents of up to 2 wt tio2 and subordinate amounts of v 62 367 ppm its b and li concentrations are mostly below 2 ppm b and 1 ppm li the presence of ti and b in the tilkerode hematite can be explained by highly saline b bearing fluids that were capable of mobilising otherwise immobile ti the mo signature of the tilkerode hematite suggests that mo was derived from the host black shale in minas gerais b and li were incorporated into the early tectonic hematite from saline fluids at relatively low temperatures aguas claras and then released during metamorphic hematite growth at higher temperatures as suggested by the foliation defining hematite without b li signature gongo soco

reconstructions of the continents around the north atlantic at about the 60th parallel abstract late carboniferous early tertiary apparent polar wander apw paths 300 40 ma for north america and europe have been tested in various reconstructions these paths demonstrate that the 500 fathom bullard et al fit is excellent from late carboniferous to late triassic times but the continental configuration in northern pangea changed systematically between the late triassic ca 214 ma and the mid jurassic ca 170 ma due to pre drift extension best fit north atlantic reconstructions minimize differences in the late carboniferous early jurassic and late cretaceous tertiary segments of the apw paths but an enigmatic difference exists in the paths for most of the jurassic whereas for the early cretaceous the data from europe are nearly non existent greenland s position is problematic in a bullard et al fit because of a late triassic early jurassic regime of compression 300 km that would be inherently required for the norwegian shelf and the barents sea but which is geologically not defensible we suggest a radically new fit for greenland in between europe and north america in the early mesozoic this fit keeps greenland locked to europe for the late paleozoic early mesozoic and maintains a reconstruction that better complies with the offshore geological history of the norwegian shelf and the barents sea pre drift a24 extension amounted to approximately 450 km on the mid norwegian shelf but with peak extension in the late cretaceous

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

red bed and basement sourced fluids recorded in hydrothermal mn fe as veins sailauf germany a la icpms fluid inclusion study the hydrothermal mn fe as vein mineralization at sailauf germany hosts a complex sequence of oxide and carbonate minerals that record a protracted fluid history the mineralization is related to a major unconformity that separates permian zechstein sedimentary rocks from underlying variscan crystalline basement the hydrothermal veins contain two principal mineralization stages which are mn oxides associated with calcite and hematite associated with mn calcite the fluid evolution of the hydrothermal system has been reconstructed from fluid inclusion petrography microthermometry and la icpms microanalysis coupled with stable isotope geochemistry of carbonate and oxide minerals the fluid inclusions are high salinity sodic calcic brines and the bulk fluid properties show no major differences between the mn oxide and the hematite stage la icpms analysis of major and trace elements demonstrates that the mineralization formed from chemically distinct fluid pulses characterized by variations in their k li b pb and zn concentrations the fluid that precipitated the mn oxide stage has anomalous pb zn and li b ratios which closely resemble fluids found in fracture fillings in red beds of the permian rotliegend basin by contrast the fluids associated with the hematite stage have pb zn and li b ratios typical of crustal fluids that were derived from interaction with crystalline basement both fluids possess characteristic element ratios including cl br but variable absolute concentrations of most metals this suggests that both fluids were modified by mixing with a common metal depleted brine that had a similar cl br ratio most likely a formation water from the overlying zechstein sedimentary rocks the sailauf mineralization provides insight into the protracted post variscan fluid evolution at the basement cover interface the compositionally anomalous fluid that precipitated the mn oxides is comparable to brines derived from interaction with red beds and likely represents the ore fluid of kupferschiefer type sediment hosted cu deposits conversely the fluid that deposited the hematite mineralization resembles fluids that typically form basement and sediment hosted pb zn deposits

application of the 187re 187os system to black shale geochronometry the decay of 187re to 187os provides a tool for determining depositional ages of black shales re and os concentrations and os isotopic compositions of whole rock samples of the bakken shale a mississippian devonian boundary black shale yield a whole rock isochron with an age of 354 49 ma this age is in agreement with the accepted age of the bakken shale 360 ma the initial 187os186os ratio of the isochron is 6 2 3 3 this value is indistinguishable from the 187os186os ratios observed in modern black sea sediments the concentration of common os in bakken shale samples is strongly correlated with total nitrogen indicating that a large fraction of the os in these samples is associated with a hydrogenous component which overwhelms any os supplied to the sediment in association with detrital material or cosmic dust the dominance of the hydrogenous component imparts a relatively homogeneous initial 187os186os ratio to the sediment at the time of deposition the degree of scatter about the isochron exceeds the degree of scatter expected from either analytical error or from the estimated degree of initial isotopic heterogeneity the pattern of scatter is consistent with postdepositional mobilization of re and or os on a small spatial scale we suggest that this mobilization may be a consequence of petroleum formation and migration in the bakken shale

lead isotope systematics of vein type antimony mineralization rheinisches schiefergebirge germany a case history of complex reaction and remobilization processes mesothermal vein type sb mineralization in the rheinisches schiefergebirge germany is characterized by two different mineralization styles which are 1 extensional quartz stibnite vein systems and 2 cu pb sb sulphosalt assemblages in overprinted pre existing pb zn veins a detailed pb isotope study of 52 representative samples from both mineralization types indicates distinct compositional patterns cu pb sb sulphosalts meneghinite boulangerite bournonite formed by reaction remobilization are characterized by pb isotope compositions 206pb 204pb 18 179 18 223 which are identical to the precursor galena 206pb 204pb 18 168 18 223 the pb isotope composition of sulphosalt minerals in these vein systems was controlled by lead inherited from pre existing galena stibnite and pb sulphosalts zinkenite semseyite plagionite formed in quartz stibnite vein systems display pb isotope ratios 206pb 204pb 18 250 18 354 which are more radiogenic than galenas from variscan pb zn ore veins 206pb 204pb 18 162 18 303 detailed small scale investigation of thrust zones hosting pb zn ores and crosscutting quartz ankerite fissure veins ramsbeck deposit indicates that the pb isotope compositions of recrystallized galena and remobilized phases boulangerite semseyite bournonite are arranged along a linear trend this is interpreted as mixing between primary galena with 206pb 204pb 18 206 and overprinting hydrothermal fluids with a more radiogenic composition 206pb 204pb 18 354 expressed by intermediate compositions 206pb 204pb 18 256 18 334 of newly formed sulphosalts the pb isotope systematics of the vein type sb mineralization is in accordance with a model of pb extraction from similar crustal sources palaeozoic sedimentary sequences at different times