paleomagnetism of the permian triassic intrusions from the tunguska syncline and the angara taseeva depression siberian traps large igneous province evidence of contrasting styles of magmatism abstract based on the detailed paleomagnetic investigation we distinguished different styles of intrusive magmatic activity in two regions of the siberian traps large igneous province lip the emplacement of intrusions in the angara taseeva depression the southern periphery of the siberian traps lip occurred as brief but intense bursts of magmatic activity that led to the emplacement of large and extensive sills we argue that this pulsating style of intrusive magmatic activity is common for the margins of the siberian traps lip we also estimated the duration of the main magmatic events as 200 250 km in diameter and dozens of thousands km2 in square on the contrary in the central part of the siberian traps lip the tunguska syncline the intrusive magmatism was more or less continuous without intense peaks of magmatic activity furthermore we obtained the first reliable magnetostratigraphic data from the volcanic section of the tunguska syncline finally we analyzed the available paleomagnetic and geochronological data from the siberian platform and suggested the correlation scheme of the studied intrusive complexes with the volcanic sequences of the siberian traps lip

assimilation of sulfate and carbonaceous rocks experimental study thermodynamic modeling and application to the noril sk talnakh region russia most of the intrusions in the noril sk talnakh region siberia are hosted in thick sedimentary sequences including abundant evaporitic and terrigenous sedimentary rocks three mafic ultramafic intrusions in this region contain unusually thick massive sulfide deposits which represent one of the world s largest economic concentrations of ni cu and pge the interaction of siberian magmas with sulfate and organic matter rich sedimentary rocks has been proposed as a possible mechanism for the origin of these exceptional sulfide deposits but the interaction process and the reaction paths have never been fully investigated here we clarify by both experimental petrology and thermodynamic modeling how sulfate and organic matter assimilation occur in mafic ultramafic magmas affecting magma composition crystallization and sulfide saturation interaction experiments were conducted at conditions relevant to the emplacement of noril sk type intrusions 1200 c 80 mpa to simulate the assimilation of sulfate and or organic compounds by ultramafic magmas we used a picrite from noril sk1 intrusion and coal and anhydrite from the area as starting materials the experimental results show that the incorporation of anhydrite into the magma occurs by chemical dissolution in the melt which increases the magma s sulfur content but suppresses sulfide saturation and reduces olivine crystallization extreme assimilation leads to sulfate saturation in the magma and high dissolved sulfur contents of 0 9 0 1 wt s conversely coal assimilation promotes sulfide segregation and magma crystallization while decreasing the dissolved h2o content of the melt and increasing the amount of coexisting fluid phase we also employed gas melt thermodynamic calculations to quantify the effect of these assimilations on the redox conditions and the s content of the magma and investigate the role of temperature pressure and initial gas content of the magma in the assimilation process we quantify how sulfate assimilation strongly oxidizes the magma and increases its s content both effects are intensified by increasing pressure from 50 to 100 mpa in this study decreasing temperature from 1350 to 1200 c in this study and decreasing amounts of fluid phase initially coexisting with the magma from 2 to 0 wt the interaction with organic matter ch in this study induces a strong reduction of the magma even for extremely low degrees of assimilation few tenths of wt and the dehydration of the melt we therefore suggest that in the noril sk talnakh district 1 additional s was supplied to mantle derived magmas by the assimilation of evaporitic rocks and was transported during magma ascent in the form of dissolved oxidized s 2 a substantial reduction of the magma inducing sulfide segregation and important crystallization then occurred due to the interaction with carbonaceous sediments this mechanism can potentially produce massive sulfide deposits by important sulfate assimilation locally higher than 3 wt caso4 and minor organic matter assimilation few tenths of wt ch however if one of the two steps does not occur or the assimilation in 1 is not large enough disseminated sub economic or no sulfide deposits are produced we conclude that exceptional conditions favoring substantial assimilation of sediments are needed to generate exceptional ore deposits like those of the noril sk talnakh district

the evolution of the mecklenburg bay environment in the holocene in the light of multidisciplinary investigations of the sediment cores abstract multi proxy studies of the sediment cores and acoustic profiles from mecklenburg bay display a more detailed picture of the evolution of the environment in the holocene studies of diatoms geochemistry grain size and radiocarbon dating clearly reveal the age and character of freshwater and marine transgressions and regressions after the final regression of the baltic ice lake a local lake and swamp environment was recorded by peat gyttja sediments this environment existed until the ancylus lake transgression dated ca 10 500 cal bp during the ancylus lake period the area remained a shallow water lake transitional isolated from the main baltic basin the first slightly brackish marine inflows confirmed by the appearance of planktonic mesohalobous and halophilous diatoms were identified at the beginning of the initial littorina sea stage and dated ca 8800 cal bp the boundary between the ancylus lake and the initial littorina sea is marked by increasing contents of biogenic silica and iron the initial littorina sea stage was characterized by increasing mesohalobous and polyhalobous diatom forms and decreasing oligohalobous species the initial littorina sea environment was recorded as a slightly brackish reservoir sporadically affected by weak marine inflows the littorina transgression appeared in the mecklenburg bay at ca 7500 7700 cal bp and is reflected by the domination of polyhalobous diatoms increasing mean grain size biogenic silica and calcium and magnesium contents the initial littorina sea was a 1500 year long period in mecklenburg bay existing until the littorina transgression the main littorina transgression first appeared in mecklenburg bay around 7700 cal bp and after a few hundred years at around 7200 cal bp in the arkona basin

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

southwest scandinavia 40 15 kyr bp palaeogeography and environmental change twelve palaeogeographical reconstructions illustrate environmental changes at the southwest rim of the scandinavian ice sheet 40 15 kyr bp synchronised land sea and glacier configurations are based on the lithostratigraphy of tills and intertill sediments dating is provided by optically stimulated luminescence and calibrated accelerator mass spectrometry radiocarbon an interstadial sequence ca 40 30 kyr bp with boreo arctic proglacial fjords and subarctic flora and occasional glaciation in the baltic was succeeded by a last glacial maximum sequence ca 3020 kyr bp with the closure of fjords and subsequent ice streams in glacial lake basins in kattegat and the baltic steadily flowing ice from sweden bordered the norwegian channel ice stream a deglaciation sequence ca 20 15 kyr bp indicates the transgression of arctic waters retreat of the swedish ice and advance of baltic ice streams succeeded by a return to interstadial conditions when ameliorated ice free conditions prevailed in maritime regions glaciers advanced through the baltic and when interstadial regimes dominated the baltic glaciers expanded off the norwegian coast the largest glacier extent was reached in the north sea around 29 kyr bp about 22 kyr bp in denmark and ca 18 kyr bp in the baltic our model provides new data for future numerical and qualitative landform based models copyright c 2003 john wiley sons ltd less

a minimum upb age for siberian flood basalt volcanism abstract establishing an accurate and precise age for siberian flood basalt volcanism is of great importance in evaluating causes for the unequaled mass extinction of flora and fauna at the permian triassic boundary we report a new minimum u pb age obtained from zircon and baddeleyite from the mineralized noril sk i intrusion that cuts the lower third of this rapidly deposited 3500 m thick volcanic sequence near noril sk this 251 2 0 3 2 ma age is within analytical error of the shrimp u pb age for zircon from the permian triassic boundary at meishan south china 251 1 3 6 ma 2 and confirms siberian basaltic volcanism as a possible contributor to the mass extinction

ni cu pge magmatic sulfide deposits in the yangliuping area permian emeishan igneous province sw china the ni cu pge sulfide deposits in the yangliuping area sw china are hosted in mafic ultramafic sills the four mineralized sills are located in the yangliuping tectonic dome and intrude devonian carbonaceous marble graphitic schist the sills are 200 300 m thick and 1 000 2 000 m in strike length and now consist chiefly of serpentinite talc schist tremolite schist and meta gabbro disseminated ni cu sulfide mineralisation occurs in the serpentinite in the lower parts of the sills massive sulfide mineralisation is located in the base of the sills and in the footwall along fractures beneath the mineralized serpentinite although the sulfide ores have been modified by hydrothermal activity there are relict cumulate textures in the disseminated sulfides indicating a magmatic origin for the ores the yangliuping intrusions and the dashibao formation have similar primitive mantle normalized trace element and platinum group element pge patterns indicating that they are derived from a common parental magma type the positive correlation between cu concentrations and cu zr ratios of the dashibao formation basalts indicates that the chalcophile elements were removed before eruption we propose that fractional crystallization of the yangliuping magma accompanied by the introduction of s and co2 from the wall rocks caused the magma to become s saturated leading to the segregation of magmatic sulfides that became enriched in ni cu pge the sills acted as conduits for the overlying dashibao formation basalts with the sulfide liquid along with early crystallizing olivine and pyroxene segregating from the magma as it passed through the conduits prior to eruption

kinetic controls on the partitioning of trace elements between silicate and sulfide liquids mass transfer between sulfide and silicate liquids is often discussed elements pge has resulted from liquation immiscible by reference to a mass ratio between hypothetical liquid reservoirs liquid phase separation of sulfide liquid from mafic or at equilibrium defined as r in an open system not at equilibrium ultramafic silicate magma a central assumption of modthe mass of silicate melt from which a growing sulfide droplet els of magmatic sulfide deposit formation is that the base appears to have scavenged chalcophile elements will depend on metals and pge are strongly partitioned into the sulfide diffusivities di and dfes of the element and of the fes component melt previous discussions of the process by which sulfide in the silicate melt respectively on the degree of supersaturation of liquids become enriched in chalcophile metals have fothe melt with fes c o on the radius a of the droplet and on the cused almost exclusively on models in which coexisting velocity v with which the droplet is advected through the melt so bodies of sulfide and silicate melt are considered to be that in equilibrium at all times the intent of this paper is to demonstrate that natural sulfide deposits preserved in igneous rocks will in many r 1 c fes o di 1 2 adiv dfes 1 2 adfesv instances record metal distributions that never attained equilibrium as a result of the kinetic constraints on metal chalcophile elements are expected to show inter element variations partitioning between phases the consequences are that in d spanning several orders of magnitude in some melts leading different elements will seem to show evidence for equito large inter element variations in effective r in a given sulfide libration at different silicate sulfide mass ratios within body these variations in effective r will lead to spatial separations single sulfide bodies i describe the time dependent evolubetween zones of maximum enrichment of chalcophile elements tion of metal distributions in silicate sulfide melt systems produced during fractional segregation of sulfide in layered intrusions starting with analytical solutions for simple boundary whereas it has proven impossible to model the generation of spatially conditions and then adapting them to more complex offset stratiform horizons in the australian munni munni layered systems as numerical models intrusion using equilibrium partition coefficients the present kinetic model reproduces the observed patterns with great fidelity

siderophile and chalcophile metal variations in tertiary picrites and basalts from west greenland with implications for the sulphide saturation history of continental flood basalt magmas sixty five million year old continental flood basalts crop out on qeqertarssuaq island and the nuussuaq peninsula in west greenland and they include 1 000 m of picritic lavas and discrete 10 to 50 m thick members of highly contaminated basalts on qeqertarssuaq the lavas are allocated to the vaigat and malig t formations of which the former includes the naujanguit member which consists of picrites with 7 29 wt mgo 80 1 400 ppm ni 5 7 9 4 ppb pt and 4 2 12 9 ppb pd the naujanguit member contains two horizons of contaminated basalts the asuk and kuganguaq which have elevated sio2 52 58 wt and low to moderate mgo 7 5 12 8 wt these lavas are broadly characterized by low cu and ni abundances average 40 ppm ni and 45 ppm cu and very low pt 0 16 0 63 ppb and pd 0 13 0 68 ppb abundances and in the case of the asuk they contain shale xenoliths and droplets of native iron and troilite the contaminated basalts from nuussuaq the b0 to b4 members are also usually ni cu and platinum group elements pge depleted the geochemical signatures especially the ratios of incompatible trace elements such as th nb of all of the contaminated basalts from qeqertarssuaq and some of those from nuussuaq record what appears to be a chemical contribution from deltaic shales that lie immediately below the lavas this suggests that the contamination of the magmas occurred during the migration of the magmas through plumbing systems developed in sedimentary rocks and hence at a high crustal level nickel cu and pge depletion together with geochemical signatures produced by crustal contamination are also a feature of siberian trap basalts from the noril sk region these basalts belong to the 0 to 500 m thick 5 000 to 10 000 km3 nadezhdinsky formation which is centered in the noril sk region a major difference between siberia and west greenland is that pge depletion in the nadezhdinsky formation samples with the lowest cu and ni contents is much more severe than that of the west greenland contaminated basalts moreover the volumes of the contaminated and metal depleted volcanic rocks in west greenland pale is significant when compared to the nadezhdinsky formation local centers rarely contain more than 15 thin flows with a combined thickness of 50 m and more typically 10 20 m so the volume of the eruptive portions of each system is probably two orders of magnitude smaller than the nadezhdinsky edifice the west greenland centres are juxtaposed along fault zones that appear to be linked to the subsidence of the tertiary delta and so emplacement along n s structures appears to be a principal control on the distribution of lavas and feeder intrusions this leads us to suggest that the greenland system is small and segregation of sulphide took place at high levels in the crust whereas at noril sk the saturation event took place at depth with subsequent emplacement of sulphide bearing magmas into high levels of the crust as a consequence it may be unreasonable to expect that the west greenland flood basalts experienced mineralizing processes on the scale of the noril sk system

sulfide saturation and magma emplacement in the formation of the permian huangshandong ni cu sulfide deposit xinjiang northwestern china the eastern tianshan orogenic belt northwestern china hosts 120 mafic ultramafic intrusions and at least six of them host significant ni cu sulfide mineralization of which the permian huangshandong intrusion is the largest the mafic ultramafic rocks of the huangshandong intrusion comprise lherzolite gabbronorite gabbro and diorite individual orebodies are composed of pyrrhotite pentlandite and chalcopyrite as disseminated to net textured or massive to semimassive sulfide mineralization oxide bearing sulfide mineralization contains 1 to 5 magmatic magnetite that has ilmenite and spinel exsolution lamellae silicate rocks and sulfide mineralization have variable whole rock platinum group elements pge 0 38 362 ppb cu 42 97 000 ppm and ni 26 33 000 ppm concentrations the mineralization is broken out into two types termed oxide rich and oxide poor the oxide rich sulfide mineralization has high pge concentrations with low 187re 188os ratios 38 9 151 whereas oxide poor sulfide mineralization has low pge concentrations with high 187re 188os 159 781 both oxide rich and poor sulfide mineralization have highly variable os values 49 189 and 30 278 respectively oxide rich sulfide mineralization contains magnetite with variable amounts of mgo tio2 al2o3 feototal cr v zn and sn indicating that they crystallized from different stages during magma differentiation we propose that the host intrusion and associated sulfide mineralization were derived from high mg basaltic magmas from a mantle source that was previously modified by subducted oceanic slab oxide poor sulfide mineralization of the huangshandong intrusion formed from a magma that underwent 0 03 sulfide removal before emplacement and was thus pge depleted oxide rich sulfide mineralization formed from magma that had much lower amounts of sulfide 0 003 removed in the early stage before entering the huangshandong magma chamber an early sulfide saturation event was likely associated with fractionation of silicate minerals in a deep staging magma chamber the second sulfide saturation event that formed the sulfide mineralization was probably triggered by selective crustal contamination and fractionation in the high level chamber where mixing of magmas and accumulation of immiscible sulfide occurred

platinum group mineralization in the rum layered intrusion scottish hebrides uk abundant and diverse platinum group minerals occur in the rum layered intrusion inner hebrides scotland platinum group minerals are associated with chromite rich horizons in both the eastern and western layered series and are enclosed by ni and cu rich sulphides or silicates the most common phases are pd cu alloys pt fe alloys laurite ru ir os s2 sperrylite ptas2 and pt pd bearing bismuthides tellurides and antimonides the mineralization on rum is due to 1 initial concentration in the parental magma linked to a high degree of melting associated with mantle plume activity and 2 localized concentration due to magma mixing and subsequent crystallization within an open system magma chamber

remobilisation of the continental lithosphere by a mantle plume major trace element and sr nd and pb isotope evidence from picritic and tholeiitic lavas of the noril sk district siberian trap russia the late permian to early triassic siberian traps have been sampled by drill core core sg 9 and from surface exposure section 1f in the noril sk region of the siberian platform russia combined major trace element and nd sr and pb isotope data on selected samples through the siberia trap offer new chemostratigraphic criteria for the identification and characterisation of two fundamentally different magma types and 9 of the 11 formations of lava developed near noril sk a lower sequence of sub alkalic basalts tholeiites and picritic basalts upwards these are the ivakinsky syverminsky and gudchichinsky formations are overlain by an upper sequence of picritic basalts and tholeiites interbedded with tuffs upwards these are the khakanchansky tuklonsky nadezhdinsky morongovsky mokulaevsky and kharayelakhsky formations the gudchichinsky and tuklonsky formations contain both picritic and tholeiitic lavas the tuklonsky formation tholeiites and picrites have moderate gd yb 1 6 1 8 low tio2 0 45 0 95 wt a significant negative ta and nb anomaly nb la 0 42 0 57 and unradiogenic nd nd chur to 4 6 in contrast both the gudchichinsky formation tholeiites and picrites have high gd yb 2 3 3 1 and tio2 1 2 2 3 wt no significant nb or ta anomaly nb la 0 8 1 1 and radiogenic nd nd chur to 7 3 the low ti and nb la high la sm and unradiogenic nd isotope signatures of the picritic tuklonsky formation lavas and the tholeiitic lavas of the upper sequence are characteristic of magmas strongly influenced by material from the continental lithosphere whereas the high ti and nb la low la sm and radiogenic nd isotope signatures of the lower sequence are more comparable to deeper asthenospheric mantle plume generated lavas similar to oceanic island basalts the lavas overlying the tuklonsky formation have mg numbers of 0 63 to 0 68 and are more evolved than the tuklonsky mg number 0 62 and have more radiogenic nd chur tuklonsky 0 03 to 4 66 mokulaevsky 0 60 to 1 61 but have many of the incompatible trace element features of the tuklonsky sky type magma these lavas show a progressive upwards decline in sio2 55 49 wt la sm 4 6 2 0 and ur sr 67 to 13 which has previously been attributed to a decrease in the proportion of crustal material contributed to the magma this paper explores and alternative model where a component of the crustal contribution might be derived from within an ancient region of the mantle lithosphere as recycled sediment rather than from the overlying continental crust

insights into ore genesis of ni cu pge sulfide deposits of the noril sk province russia evidence from copper and sulfur isotopes abstract combined cu s isotope data for ni cu pge sufides from the economic deposits hosted in the noril sk 1 talnakh and kharaelakh intrusions from the subeconomic deposits in the chernogorsk zub marksheider and vologochan intrusions and from the non economic occurrences in the nizhny talnakh intrusion in the noril sk province russia and the j m reef in the stillwater complex usa are presented for the first time most sulfide samples including the ores from the talnakh intrusion and the stillwater complex have a restricted range of 65 cu values from 1 1 to 0 whereas those from the kharaelakh and noril sk 1 intrusions have more variable 65 cu values of 2 3 to 1 0 samples from the three economic deposits in the noril sk province have distinct mean 65 cu values of 1 56 0 27 for kharaelakh 0 55 0 41 for talnakh and 0 23 0 28 for noril sk 1 consistent with those for carbonaceous chondrite and iron meteorites the variation of 65 cu values is interpreted to represent a primary signature of the ores although a magmatic fractionation of cu isotopes and or assimilation from an external source cannot be ruled out particularly in the case of the kharaelakh ores collectively the eight investigated intrusions have an overall sulfur 34 s range from 0 7 to 13 8 disseminated and massive ores of the same intrusion have similar 34 s values the disseminated and massive ores of the khraelakh intrusion have a mean 34 s value of 12 57 0 54 and 12 76 0 42 respectively which are distinctly different from those of the disseminated 10 97 0 44 and massive ores 10 88 0 77 of the talnakh intrusion the different 34 s values of the intrusions may be attributed to sulfur fractionation in deep seated magma chambers rather than at shallow levels or the present emplacement site the mean 34 s value of the disseminated ores from the subeconomic ni cu pge deposits and non economic occurrences spans over 10 5 averaging 0 39 with a standard deviation of 1 55 for the highly contaminated zub marksheider rocks 6 38 1 89 for nizhny talnakh 6 90 1 17 for vologochan and 10 86 0 43 for chernogorsk samples from the zub marksheider intrusion have mantle like s isotope signatures consistent with a deep seated origin although individual mineralized instrusions have a restricted range the overall trend they define of falling 34 s with rising 65 cu values might be a useful indicator of the economic potential of ni cu pge sulfide deposits

darss sill as a biological border in the fossil record of the baltic sea evidence from diatoms abstract biostratigraphical and palaeoecological analyses of cores along a transect from femer belt to the arkona basin reveal that north sea waters began to enter the western baltic sea between 8600 and 8400 calibrated years bp studies of diatoms indicate that mecklenburg bay was characterised by slightly brackish water conditions between 8400 and 8000 cal years bp at around 8000 cal years bp increasing salinity is indicated by a strong dominance of the diatoms paralia sulcata and dimeregramma minor some centuries later another diatom assemblage appeared and became dominant in mecklenburg bay this assemblage includes hyalinella lateripunctata and pravifusus hyalinus species typical of shallow water areas along the atlantic coast today at this time the first marine molluscs made their appearance the oldest shell of a marine mollusc found in our material is dated to 7600 cal years bp the associated assemblage that includes adult specimens of the gastropod aporrhais pespelicani indicates higher salinities than today during the littorina sea stage a marine diatom flora with p sulcata catenula adhaerens and d minor crossed the darss sill and became widely distributed in the arkona basin pomeranian bay and the baltic sea proper in contrast taxa indicative of the hyalinella lateripunctata p hyalinus assemblage are only found west of the darss sill in femer belt and mecklenburg bay apparently the darss sill threshold has been acting as an important salinity border from around 7800 cal years bp until today

sulfide saturation mechanisms in gabbroic intrusions in the nipigon embayment the seagull and kitto intrusions in the nipigon embayment of northwestern ontario were studied to gain an understanding of the processes involved in sulfur saturation of the mafic to ultramafic magmas leading to the formation of platinum group element pge concentrations profiles of sulfur copper nickel gold palladium and platinum concentrations as a function of depth revealed that sulfur saturation occurred at the base of the seagull intrusion a higher grade horizon occurs well above the base of the intrusion suggesting that a reef type of process was significant here and possibly in the kitto intrusion as well olivine compositions indicate that in both cases the parental magmas were undersaturated with respect to sulfur sulfur neodymium samarium and rubidium strontium isotopic data suggest that assimilation of country rock and sulfide played a role especially in the formation of basal concentrations of pges

a paleomagnetic record from lake lama northern central siberia abstract two cores from lake lama northern central siberia with lengths of 19 and 11 m respectively were subjected to detailed magnetostratigraphic investigations directions of the characteristic remanent magnetisation chrm were derived from vector analysis of the results from alternating field a f demagnetisation yielding records for the last 18 000 years bp the sediments show a distinct change in sedimentation pattern at around 14 500 years bp from a highly variable to a monotonous sedimentation with anoxic conditions in the lake sediments during the last 11 500 years bp the oxic anoxic boundary is reflected in all rock magnetic parameters measured and the magnetic mineral fraction is affected by reductive dissolution of iron bearing minerals here mainly magnetite therefore no record of relative paleointensity could be achieved but as intra and inter lake comparison of the obtained inclination and declination records have shown the directions of the geomagnetic field recorded in the sediments from lake lama were not severely affected by the partial dissolution of the remanence carrying minerals

environmental evolution of western baltic sea in the holocene in the light of multidisciplinary investigations of sediments cores from arkona basin abstract a multidisciplinary investigation performed on gravity cores supplemented by a new radiocarbon dating of macrofossils outlined the environmental evolution of arkona basin in the holocene studies comprising the analysis of diatoms geochemistry grain size and radiocarbon dating clarified the knowledge about the age and environmental changes during freshwater and marine transgressions and regressions the acoustic profiling method allowed proper interpretation of the analysis results from sediment cores and created a proper lithostratigraphic model of the investigated basin baltic ice lake and yoldia sea sediment layers were identified acoustically and cores penetrated the final regression surface of the baltic ice lake the analyses of cores concentrated on ancylus lake and littorina sea sediments two phases of the ancylus lake stage were identified the peaks of loss on ignition in the cores observed as a strong acoustic reflector were identified as a marker of ancylus lake regression between the first high water level phase and the second shallow water phase the age of onset of littorina transgression was estimated at around 7000 7200 cal bp and was younger than some previous estimations the retrieved age confirmed the suggestion that the marine environment appeared first in mecklenburg bay and then after a few hundred years in arkona basin as an intensive transgression the appearance of littorina sea revealed a fast shift of the environment from lacustrine to marine the first phase of the littorina stage was recognised as a rapidly increasing water level and high energy environment the second showed rapidly increasing salinity in the calmer conditions of sedimentation

a submerged mesolithic lagoonal landscape in the baltic sea south eastern sweden early holocene environmental reconstruction and shore level displacement based on a multiproxy approach abstract remains of a submerged landscape around the mouth of a small river are preserved off the baltic sea coast at havang in south eastern sweden organic rich sediment ridges with abundant wood remains and archaeological artefacts extend 3 km from the modern coast to depths of at least 20 m below the present sea level this exceptionally well preserved material gives evidence of a lagoonal environment surrounded by a pine dominated forest which was inhabited by mesolithic humans during two low stand phases of the baltic basin from the yoldia sea stage to the initial littorina sea stage c 11 700 8000 cal bp as part of ongoing efforts to reconstruct the local landscape development and to refine the shore level displacement history during the early holocene a 3 m sediment sequence was collected at 8 m b s l and dated by radiocarbon analysis a multi proxy stratigraphic approach was applied to the sediment record including pollen diatom organic and inorganic elemental analyses this stratigraphic dataset is explored in the context of detailed bathymetry of the area based on multibeam echo sounding and surveillance and sampling of artefacts by divers the investigated sediment sequence reflects a stable highly productive lagoonal environment with an unusually high sediment accumulation rate at c 9100 8600 cal bp the uppermost 1 m part of the sequence represents a destabilized depositional environment interpreted as reflecting an increased influence of brackish water due to the approaching coastline during the littorina transgression the shore level displacement in the area is characterized by rapid water level fluctuations following a regression to around 22 m b s l during the yoldia sea stage the ancylus transgression reached a maximum of 2 m b s l followed by a second regression to a low stand at 12 m b s l during the initial littorina sea stage several unprecedented archaeological findings made in the study area are presented and discussed including stationary fishing constructions dated to c 9100 8400 cal bp these constructions the oldest known in northern europe indicate extensive riverine and lagoonal fishing previously not recorded during the mesolithic in sweden furthermore bones and antlers of red deer with slaughter marks and a unique pick axe made of elk antler provide evidence of human exploitation of terrestrial resources the havang site shows the strong potential of submerged landscapes as palaeoecological source materials and demonstrates the importance of resources at coastal settings near river mouths for mesolithic communities

late pleistocene and early holocene paleogeography of the darss sill area southwestern baltic abstract today about 73 of the water exchange between the baltic and the north sea takes place through the darss sill area in hydrographic terms the darss sill is a major morphological unit separating the deeper areas of the mecklenburg bay and the arkona basin from each other it is characterized by an average water depth of 16 m the main bathymetric features are the gedser reef with a water depth of less than 10 m and the kadet channel which has a maximum water depth of 32 m according to previous authors there are two different ice marginal lines between falster denmark and the darss peninsula germany the recent kadet channel is regarded as a large glacial valley cutting the ice marginal lines joint danish and german investigations in the darss sill area 1989 1991 indicate the existence of only one marginal line in this region which is represented by a till cropping out in the area between falster and the german coast the formation of the marginal line ca 13 500 bp caused a damming of a pre existing subglacial drainage system in the gedser reef area southeast of the recent kadet channel glaciofluvial drainage occurred towards the ne through a deep channel into the baltic ice lake immediately after the retreat of the ice during the baltic ice lake transgression the channel was filled by sandy sediments from sources east of the investigated area this accumulation process resulted in the blocking of the channel at the time of the baltic ice lake highstand maximum at this time occasional overflow in the kadet channel area must have started the main erosion and deepening of the kadet channel must however be ascribed to the ancylus lake overflow

a reconnaissance 40ar39ar geochronologic study of ore bearing and related rocks siberian russia abstract 40 ar 39 ar age spectra of biotite from a mineralized vein in the ore bearing noril sk i intrusion and from picritic like gabbrodolerite from the weakly mineralized lower talnakh intrusion show that these bodies were emplaced at 249 2 ma which is not significantly different from the age of the permian triassic boundary the ore bearing intrusions postdate the lower third of the flood basalt sequence in the noril sk area and on the basis of geochemistry can best be correlated with lavas slightly younger than those which they cut thus flood basalt was erupted at the time of the permian triassic mass extinction event although its role in this event is as yet ill defined additional new 40 ar 39 ar age data for a group of intrusive and extrusive rocks on the western margin of the siberian craton indicate that mafic magmatism extended over a period of several tens of million years whereas paleomagnetic data suggest that the bulk of the siberian flood basalt sequence near noril sk has been erupted in only a million years or so 40 ar 39 ar ages of plagioclase from early flood basalt flows are about 2 younger than those obtained for biotite from the crosscutting noril sk i intrusion probably because of slight alteration and argon loss from the plagioclase

geology and geochemistry of intrusions and flood basalts of the noril sk region ussr with implications for the origin of the ni cu ores geochemical studies indicate that five principal magma types characterize the 3 8 km vertical thickness of flood basalt of the noril9sk region from base to top these are 1 a fractionated type with alkalic affiliations ivakinsky and syverminsky 2 an ni rich suite including picritic basalt gudchichinsky 3 a primitive but ni depleted suite with fiat rare earth element ree profiles and also including picritic basalts tuklonsky 4 a light ree enriched crustally contaminated suite lower nadezhdinsky nd 1 above 4 there is a transitional suite upper nadezhdinsky nd 2 and morongovsky mr 1 and mr 2 which is overlain by the fifth type a second primitive suite without picrites mokulaevsky similar but not identical in its chemistry to the tuklonsky type this is followed by tuffs and basalts of the kharayelakhsky kumginsky and samoyedsky suites which are largely composed of similar uncontaminated tholeiitic magma the latter three suites have not been studied by us intrusions of the region fall into five main groups 1 alkalic intrusions 2 ti rich dolerite dikes 3 dolerite sills and dikes 4 differentiated bodies not related to ore junctions and 5 differentiated bodies related to ore junctions the ni cu ores are associated with ni and cr rich type 5 olivine rich intrusions with flat ree profiles that are geochemicaly similar to the mokulaevsky magma light ree enriched ni and cr poor olivine rich type 5 intrusions with uneconomic mineralization occur closely associated with the strongly mineralized variants and resemble geochemically the basalts transitional between the lower nadezhdinsky and upper morongovsky they are cut by the strongly mineralized bodies indicating that the latter are of late morongovsky to mokulaevsky age the mineralized intrusions are associated with about 1 5 to 1 10 of their mass in sulfides this is a factor of 25 to 50 more than could have been carried in solution and deposited by in situ liquation from the magma of these intrusions the platinum group element pge concentrations in the ores require that the sulfides giving rise to them equilibrated with 15 to 200 times more magma than is represented by the intrusions much of the ore is very massive and crosscuts the host intrusions the sequence of igneous activity and mineralization in the immediate vicinity of noril9sk and talnakh from the base of the nadezhdinsky upward is thus interpreted to be 1 extrusion of highly crustally contaminated ni and cu poor basalt 2 extrusion of a series of basalt flows each progressively less contaminated and less ni and cu depleted than the preceding one accompanied by intrusion of contaminated ni depleted magma with weak mineralization 3 extrusion of uncontaminated ni and cu rich basalt accompanied by intrusion of uncontaminated ni rich magma with strong mineralization followed very closely by introduction of associated massive ore and 4 continued extrusion of ni and cu rich basalt it is proposed that crustal contamination of the original ni and cu rich magma occurred at the top of a vertically extensive fault controlled magma chamber and caused segregation of immiscible sulfides with a low r factor these depleted this magma in chalcophile elements and settled deeper in the chamber as they settled they reacted with less contaminated magma scavenging additional chalcophile elements they finally came to rest near the base of the chamber to form a zone of sulfide and thus chalcophile element enriched magma eruption and in some instances intrusion of progressively stratigraphically lower less contaminated and thus less depleted layers in the chamber gave rise to the observed sequence of basalts and intrusions the answer to the strong enrichment in ni cu and pge associated with the ore bearing intrusions is that these metals came from the magma that is now represented by the depleted basalts

hydrographic thresholds in the western baltic sea late quaternary geology and the dana river concept abstract since the final weichselian deglaciation the water exchange between kattegat and the baltic sea and hence the palaeogeographical development of the western baltic has been controlled by a number of sills major thresholds are found at the southern entrance of the great belt and in the darss sill area the easternmost of these structures is formed by late weichselian sands at a level of 24 m below present sea level bsl at the falster rugen sand plain a second threshold consisting of till was found within the kadet channel at a level of 23 24 m bsl thus we exclude water exchange between mecklenburg bay and the arkona basin at levels below 24 m since the end of the pleistocene a high resolution sediment echosounder survey at the triple junction area of langeland channel vejsnaes channel and winds grave channel showed outcropping glacial deposits narrow channels incised at a level below 25 m bsl are filled partly with fine grained organic rich late and postglacial sediments assuming no substantial crustal movements in this area in the holocene no ancylus lake drainage at a level deeper than 25 m bsl is likely to have occurred here

changes in the flow of atlantic water into the arctic ocean since the last deglaciation evidence from the northern svalbard continental margin 80 n 1 the svalbard archipelago is located in the high arctic 76 80 n within the northernmost reach of the west spitsbergen current which is the continuation of the north atlantic current in this specific setting close to the polar front even small variations in the current system are expected to give large and distinct signals in paleoceanographic parameters thus the svalbard area is ideal for monitoring the past history of the inflow of atlantic water to the arctic ocean we have studied sediment core np94 51 taken outside the mouth of the hinlopen strait on the northern svalbard shelf the paleoceanographic development of the last deglaciation and the holocene has been reconstructed using benthic and planktonic foraminifera oxygen isotopes and ice rafted detritus the results show that the first strong subsurface inflow of atlantic water to the arctic ocean after the last glacial maximum commenced at 12 6 14c kyr b p circa 15 000 calendar cal years b p during the bolling allerod interstadial during the younger dryas polar conditions prevailed at the surface with extensive sea ice cover and the inflow of atlantic derived water was generally diminished the inflow of more saline but still cold atlantic water was relatively strong during the early holocene and caused intensified seasonal biological productivity the atlantic water inflow declined gradually during the mid holocene between 4500 and 1100 cal years b p the inflow was very weak and the bottom waters over the northern svalbard margin were cold and of lower salinity during the last 1000 years climatic conditions improved such that the subsurface inflow of atlantic derived water increased however the surface waters were still cold

early holocene history of the baltic sea as reflected in coastal sediments in blekinge southeastern sweden integrated palaeoecological studies of two fiord sediment sequences in the province of blekinge se sweden covering the time span 11 000 5000 cal bp reveal the timing and the environment for the ancylus lake littorina sea transition 9800 8500 cal bp the first ingression of saline water into the baltic sea through the danish straits occurred earlier than formerly assumed new evidence particularly mineral magnetic and palaeobotanical analyses demonstrate that on the general trend of the eustatically caused littorina transgression several minor fluctuations of the water level can be identified between 8500 and 5000 cal years bp a distinct regression phase around 8 100 cal bp is correlated with the greenland ice core cold event dated to 8200 ice core years bp this is described as a regional climatic catastrophe for the baltic sea region the coastal stratigraphy is compared with the offshore stratigraphy earlier studied a tentative shore displacement curve for early and middle holocene is presented

noril sk talnakh cu ni pge deposits a revised tectonic model the noril sk mining district is located at the northwest margin of the tunguska basin in the centre of the 3 000 4 000 km siberian continental flood basalt cfb province this cfb province was formed at the permo triassic boundary from a superplume that ascended into the geometric centre of the laurasian continent which was surrounded by subducting slabs of oceanic crust we suggest that these slabs could have reached the core mantle boundary and they may have controlled the geometric focus of the superplume the resulting voluminous magma intruded and erupted in continental rifts and related extensive flood basalt events over a 2 4 ma period cu ni pge sulfide mineralization is found in olivine bearing differentiated mafic intrusions beneath the flood basalts at the northwestern margin of the siberian craton and also in the taimyr peninsula some 300 km east of a triple junction of continental rifts now buried beneath the mesozoic cenozoic sedimentary basin of western siberia the noril sk i and talnakh oktyabr sky deposits occur in the noril sk kharaelakh trough of the tunguska cfb basin the cu ni pge bearing mineralized intrusions are 2 3 km wide and 20 km long differentiated chonoliths previous studies suggested that parts of the magma remained in intermediate level crustal chambers where sulfide saturation and accumulation took place before emplacement the 5 7 km thick neoproterozoic to palaeozoic country rocks containing sedimentary cu mineralization and evaporites may have contributed additional metal and sulfur to this magma classic tectonomagmatic models for these deposits proposed that subvertical crustal faults such as the northeast trending noril sk kharaelakh fault were major trough parallel conduits providing access for magmas to the final chambers however geological maps of the noril sk region show that the noril sk kharaelakh fault offsets the mineralization which was deformed into folds and offset by related reverse faults indicating compressional deformation after mineralization in the late triassic to early jurassic in addition most of the intrusions are sills not dykes as should be expected if the vertical faults were major conduits a revised tectonic model for the noril sk region takes into account the fold structure and sill morphology of the dominant intrusions indicating a lateral rather than vertical emplacement direction for the magma into final chambers taking into account the fold structure of the country rocks the present distribution of the differentiated intrusions hosting the noril sk i and talnakh oktyabr sky deposits may represent the remnants of a single 60 km long deformed and eroded palm shaped cluster of mineralized intrusions which are perceived as separate intrusions at the present erosional level the original direction of sill emplacement may have been controlled by a northeast trending paleo rise which we suggest is present at the southeastern border of the noril sk kharaelakh trough based on analysis of the unconformity at the base of the cfb the mineralized intrusions extend along this rise which we interpret as a structure that formed above the extensionally tilted block in the metamorphic basement geophysical data indicate the presence of an intermediate magma chamber that could be linked with the talnakh intrusion in turn this t shaped flat chamber may link with the yenisei khatanga rift along the northwest trending pyasina transform fault which may have served as the principal magma conduit to the intermediate chamber it then produced the differentiated mineralized intrusions that melted through the evaporites with in situ precipitation of massive disseminated and copper sulfide ore the noril sk kharaelakh crustal fault may not relate to mineralization and possibly formed in response to late mesozoic spreading in the arctic ocean

correlation of the permian triassic ore bearing intrusions of the norilsk region with the volcanic sequence of the siberian traps based on the paleomagnetic data

the behaviour of platinum group elements in basalts from the east greenland rifted margin the continental flood basalts of the east greenland volcanic rifted margin were extruded during continental breakup above the ancestral iceland mantle plume at 55 ma three distinct magma types the low ti high ti and very high ti series lts hts and vhts respectively are found intercalated in the 6 km thick plateau lava sequence incompatible trace elements indicate that the lts are derived from a more depleted mantle source compared to hts and vhts the lts is characterised by increasing cu 105 to 248 ppm and pd 7 to 24 ppb constant cu pd ratio 10 000 and decreasing ir 1 1 to 0 05 ppb and ru 1 8 to 0 3 ppb concentrations during magmatic differentiation 16 to 7 wt mgo the constant cu pd ratio reflects silicate and chromite dominated fractionation without concurrent segregation of sulphide s undersaturated differentiation is also indicated in the hts which also displays increasing pd 6 16 ppb and decreasing ir concentrations 1 to 0 05 ppb during differentiation and the cu pd ratios for the entire series average 21 000 however some hts samples have elevated cu pd ratios up to 33 000 cu pd ratios in the hts do not correlate with mgo and this is interpreted to reflect varying cu pd ratios of hts parental magmas rather than s saturated differentiation during s undersaturated differentiation of the lts and hts pt pd ratios decrease from 1 3 to 0 11 and 1 1 to 0 2 respectively which indicates that pd is much more incompatible than pt during s undersaturated differentiation the vhts consists exclusively of highly evolved samples with low mgo 6 6 6 1 wt and pd ir ratios 98 228 here cu pd ratios increase from 17 500 to 35 000 with decreasing cr concentrations which indicate that these magmas experienced silicate fractionation with concurrent segregation of sulphide the lts represent melting of a depleted source and show high pge concentrations and constant cu pd ratios during s undersaturated differentiation melting of a normal depleted upper mantle source generates s saturated melts morb and the depleted lts source is therefore considered an extraordinary s poor component within the ancestral iceland plume of the three series the vhts contain the largest contribution from enriched mantle portions the vhts have similar pge but much higher nb concentrations for instance compared to the most evolved lts and hts samples indicating that the enriched source contributes nb but not pge

geo acoustic modelling of late and postglacial sedimentary units in the baltic sea and their acoustic visibility abstract acoustic profiling methods are commonly used in the geosciences to obtain knowledge about the sedimentary structures of marine deposits however their interpretation and the correlation of acoustic reflectors with sedimentological boundaries remain difficult the gradient in acoustic impedance determines the intensity of acoustic reflectors which are not necessarily sedimentary boundaries suitable geo acoustic models that cover a wide range of sediment types have not yet been developed for the baltic sea based on comprehensive investigations of sediment cores from mecklenburg bay and the arkona basin we developed geo acoustic models that enable the transfer of laboratory p wave velocity measurements to in situ conditions while considering changes in pressure salinity temperature and the frequency dependence of the p wave velocity i e acoustic dispersion this modelling allows the calculation of the wet bulk density and in situ p wave velocity from which the acoustic impedance is calculated from core logging and selected sedimentological data such as the water content loss on ignition and grain size precise plotting of core data into the acoustic profiles is now possible and represents a crucial step towards the interpretation of these profiles modelled p wave velocities are used to convert two way travel time to depth the average sedimentological parameters for the different development phases of the baltic sea are calculated using geo statistical methods and may allow for rough p wave estimations if core logging data are not available

evidence for as contamination and the partitioning of pd into pentlandite and co platinum group elements into pyrite in the fazenda mirabela intrusion brazil the fazenda mirabela intrusion in brazil hosts two zones of mineralization the santa rita ni cu sulfide ore zone occurring predominantly in an orthopyroxenite layer and an underlying basal platinum group element pge anomaly hosted in s poor dunite we show that in the northern and southern marginal zones of the intrusion pt pd ni cu fe bi te 2 minerals are accompanied by as bearing platinum group minerals pgm sperrylite ptas2 and irarsite rhirpt ass these as bearing pgm are extremely rare in the central zone of the intrusion suggesting that as has been introduced into the margins of the intrusion from the country rocks via crustal assimilation or synmagmatic hydrothermal processes other pgm and precious metal minerals pmm including hessite ag2te pd ag tellurides electrum and native au are observed in the santa rita ore zone and do not show any lateral variation in the semimetal and s poor dunite hosting the basal pge anomaly pge are predominantly retained in the base metal sulfides and only minor pge alloys are present in this s poor dunite pt au and semimetals partitioned into a fractionated cu rich liquid which formed during the crystallization of monosulfide solid solution mss and was largely removed by high temperature magmatic fluids palladium was not affected by this process and significant concentrations of pd are identified in pentlandite suggesting that pd preferentially partitioned into mss as it crystallized and subsequently pentlandite as it exsolved pyrite in the santa rita ore zone is co rich and contains higher concentrations of ipge os ir ru and rh than pyrrhotite and pentlandite suggesting that pyrite has not replaced and inherited the pge concentrations of these sulfides the pd poor nature of pyrite also indicates that it has not replaced pd rich pentlandite it is proposed that the ipge and co preferentially partitioned into pyrite as it exsolved from mss

biomarkers and geochemical indicators of holocene environmental changes in coastal lake sarbsko poland organic rich samples from the holocene sedimentary sequence of lake sarbsko were investigated to reconstruct variations in the aquatic system in response to environmental change the aims were to i identify organic matter om sources ii examine changes in soluble om composition in relation to fluctuations in limnological conditions and iii validate the sensitivity of organic geochemical indicators in tracing environmental changes diatom frustules are abundant in all samples alginite macerals and terrigenous organic matter further contribute to the sedimentary om organic petrography total organic carbon toc n ratio values and high content of biogenic silica sio2 biogenic argue for a predominant algal source of om in contrast the n alkane distributions high relative abundance of c29 steroid hydrocarbons and high content of detrital quartz in the sediments provide evidence for the input of terrigenous material as a major om source within the basin the terpenoid biomarker composition indicates a contribution from conifers and angiosperms from the diterpenoids in the samples a contribution from species of the coniferales family pinaceae is concluded toc s and mg ca values as well as steroid hopanoid concentration ratios reflect enhanced water salinity in this coastal lake due to ingression of brackish water from the baltic sea during the atlantic and sub atlantic periods as indicated by the positive relationship between d 13 c of toc and mg ca d 13 c values are influenced by changing contribution of marine vs freshwater phytoplankton additional isotopic heterogeneity in d 13 c may result from differences in terrigenous om supply vs autochthonous om production in the lake the isotopic composition of calcites supports the establishment of freshwater conditions in the lake during the sub boreal period pristane phytane and fe mn ratios are interpreted to reflect differences in the redox conditions oxygenation of bottom waters was temporarily variable with highest levels of oxygen availability during the sub boreal freshwater lake high contents of hopanoid hydrocarbons argue for enhanced microbial activity in the water column and sediment the occurrence of 2b methyl hopanes is related to the presence of cyanobacteria or methylotrophic bacteria

late paleozoic mafic ultramafic intrusions in southern central asian orogenic belt nw china insight into magmatic ni cu sulfide mineralization in orogenic setting abstract the mafic ultramafic intrusions hosting magmatic ni cu sulfide ore deposits usually present within the precambrian cratons and on their margin have been extensively studied whereas those occurring within the phanerozoic orogenic belts have received little attention the southern margin of the central asian orogenic belt is a region of late paleozoic mafic ultramafic intrusions emplaced during post orogenic stage in order to recognize the mineralization features this study compares barren or weakly mineralized mafic ultramafic intrusions in the beishan with those hosting ni cu sulfide ore deposit in the altay and eastern tianshan in petrology mineralogy and geochemistry aspects several mineralization features can be recognized with respects to petrology mineralogy and geochemistry from comprehensive comparisons among the mineralization indicators we highlight strong alteration accompanying sulfide emplacement post erosion exposure of magma conduit abundant primary hydrous minerals and potential transportation mechanism of ore forming elements other indicators are the presence of orthopyroxene and pyroxenite for potential sulfide formation through crystal fractionation restricted fo and ni ranges in olivines for sulfide segregation and some other special geochemical characteristics related to crustal contamination the variation in mineralization could be ascribed to different degrees of partial melting crustal assimilation and subduction related modification of a mantle source we suggest that the ni cu sulfide mineralization of mafic ultramafic intrusions within orogenic belts is remarkably different from that of cratonic and continental marginal settings in respects of petrogenesis and mineralizing mechanism magmatic conduit type ni cu sulfide ore deposit is a target for future prospecting and exploration for mafic ultramafic intrusions in the orogenic belts

a review of the history of the baltic sea 13 0 8 0 ka bp abstract the dynamic history of the baltic sea during the millennia following the last deglaciation has been one of the main topics for many generations of quaternary geologists around the baltic sea based on the present state of knowledge and certain hypotheses a model for the development during the baltic ice lake yoldia sea and ancylus lake stages are presented the oresund strait was the threshold of the initial stage of the baltic ice lake and was eroded down to bedrock as a result of the isostatic uplift the emerging threshold forced the baltic ice lake to rise above sea level at ca 12 0 ka bp this gradual up damming ended at ca 11 2 ka bp when the large glacial lake was lowered 5 10m by possible subglacial drainage at mt billingen a glacial readvance during the younger dryas ended a ca 400 year long land bridge between sweden and the continent by blocking the former drainage route once again the baltic ice lake had to rise above sea level to be drained over the oresund strait at ca 10 5 ka bp a gradual ice recession began and 200 years later when the receding ice sheet could not withhold the up dammed water masses the final drainage of the baltic ice lake occurred which rapidly lowered the water level within the baltic basin with ca 25 m and ended the baltic ice lake stage the next stage the yoldia sea was characterized by a complex pattern of relative sea level changes with large differences within the baltic basin a very restricted baltic sea in the south and thus an extensive landbridge at ca 9 9 ka bp a short 100 200 years saline ingression is seen in the baltic sediment records from stockholm in the north to the southernmost parts of the yoldia sea the gradually shallower strait in south central sweden the narke strait ended the saline influence 300 400 years later the two remaining outlets west of lake vanern gota alv and otteid steinselva had become too shallow to swallow the outflowing yoldia sea waters at this stage the baltic lake vanern level could thus not fall in pace with the relative sea level fall outside the outlet areas this was the isolation of lake vanern and the baltic from the sea and the beginning of the ancylus lake since the water depth of the larger gota alv outlet had to be more or less maintained the ancylus lake level had to rise in pace with the uplift of the outlet region this caused a significant and rapid transgression 10 30 m in ca 300 years in the southern baltic which flooded large areas with recently immigrated pine forests since the oresund strait during the yoldia sea stage had been uplifted more than southerly areas the ancylus transgression ended with a new drainage pathway at ca 9 2 ka bp through the darss sill area in the southern baltic and northwards through the store belt strait this so called dana river had cut off the former large land bridge the quaternary deposits of this new threshold were eroded and a fairly rapid regression set in at ca 9 0 ka bp the dana river had eroded down to the sea level which isolated lake vanern from the ancylus lake and created a land bridge between southern sweden and northwards ca 800 years later when the sea level rose above the oresund threshold marine water could enter the baltic and at ca 8 0 ka bp brackish water characterized the southern baltic this marks the end of the ancylus lake

a new genetic model for the giant ni cu pge sulfide deposits associated with the siberian flood basalts the kharaelakh intrusion is one of several sill like multiphase gabbroic intrusions that host world class ni cu pge deposits in the noril sk talnakh region the sulfide ores of the kharaelakh intrusion are characterized by elevated 34s values 10 12 and high pge concentrations e g up to10 ppm pt the 34s values require addition of crustal s with elevated isotope ratios such as evaporite bearing country rocks 34s 20 and r factors magma sulfide mass ratios of 2 000 if pt content in the magma is similar to the values in the coeval most undepleted lavas 10 ppb such a discrepancy can be explained by sulfide resorption by a new flux of mantle derived magma into a deep staging chamber to form pge enriched magma interaction of the pge enriched magma with evaporite bearing country rocks in the plumbing system at higher crustal levels could have produced sulfide liquids with high pge contents as well as elevated 34s values mass balance calculations indicate that 0 9 wt percent anhydrite assimilation from evaporite bearing country rocks is required to explain the elevated 34s values of the sulfide ores this model although developed purely based on data from the kharaelakh deposit can also be applied to other coeval ni cu pge deposits for the coeval noril sk i and talnakh deposits different depths of anhydrite assimilation in the respective plumbing systems are required this model differs from the previously proposed models in detail but reenforces the idea that chalcophile element depletion in continental flood basalts is a useful exploration tool for ni cu pge deposits associated with coeval subvolcanic intrusions

precious metal enrichment at low redox in terrestrial native fe bearing basalts investigated using laser ablation icp ms primary native fe is a rare crystallizing phase from terrestrial basaltic magmas requiring highly reducing conditions fo2 iron wustite buffer in order to form reducing conditions in basaltic magmas can be achieved through assimilation of carbonaceous crustal material which leads to formation of an immiscible molten c rich native fe alloy liquid if this liquid also contains sufficient sulfur it can undergo further division into conjugate fe c rich and a fe s rich immiscible melts that can effectively scavenge the highly siderophile elements hse re au and the platinum group elements pge pd pt rh ru ir os as well as ni and cu to economic abundances three localities are known globally where native fe bearing mafic rocks occur 1 paleocene basalts of disko island west greenland 2 a miocene lava of the buhl basalts germany and 3 mafic intrusions associated with the late permian siberian flood basalts in this contribution we report major and minor element compositions and hse concentrations for the main alloy phases feni metal and cohenite and sulfide for all three known global occurrences of native fe bearing basalt total hse abundances in metal grains obtained by laser ablation inductively coupled plasma mass spectrometry la icp ms are lowest in the buhl basalt 0 05 ppm intermediate in the disko island basalts 4 8 ppm and highest the siberian khungtukun and dzhaltul intrusions 10 30 ppm these differences demonstrate that while native fe formation is the result of carbonaceous crustal assimilation hse enrichment is not ubiquitous during this process the siberian occurrences are characterized by pt pge ppge pt pd enrichment relative to the ir pge ipge rh ru ir os consistent with models of early stage fractionation of olivine chromite and metallic ipge in staging magma reservoirs prior to the addition of c rich crustal materials in the shallow crust relative to noril sk ni cu pge sulfide ores the siberian native fe basalts are enriched in the ppge relative to the ipge but exhibit ru enrichments in contrast disko island native fe rocks do not show significant fractionation of the ppge from the ipge but have positive re and ru anomalies and high os ir ratios to reconcile these observations we present a general model where some parental melts experienced early stage crustal assimilation in staging magma reservoirs prior to reduction by carbon rich materials e g khungtukun dzhaltul whereas basaltic parental melts to disko island and buhl solely experienced interaction with carbonaceous material resulting in extensive devolatilization native fe segregation and native fe formation

changes of sea level landscape and culture a review of the south western baltic area between 8800 and 4000bc abstract the global warming at the end of the last glacial period led to a sea level rise which induced substantial long term landscape changes in the southwestern baltic sea during the preboreal and boreal periods this region bordering on the ancylus lake in the east was dry land with numerous lakes and rivers however with the beginning of the littorina transgression around 6700 bc during the atlantic period the area became connected to the ocean people settling along the coast of the former ancylus lake mesolithic hunter gatherers continuously had to adapt to rapid changes the littorina transgression made a new source available to man the young baltic sea important settlement sites were founded in the coastal regions and were consumed one by one by the constantly rising sea level at the time of the decline of the sea level rise and the beginning consolidation of the coast lines a socially motivated turn towards a productive economy started hunting and fishery were widely replaced by agriculture and stock farming to understand the interplay between all of these developments it is necessary that scientists from a variety of disciplines undertake collective investigations this paper presents first culture historical palaeozoological palaeobotanical palaeoecological and palaeogeographical results yielded by from the multidisciplinary research group sincos sinking coasts and uses these to create a new comprehensive picture of the development of the south western baltic sea region during the ancylus lake and littorina sea stages

early holocene brackish and marine facies in the fehmarn belt southwest baltic sea depositional processes revealed by high resolution seismic and core analysis holocene stratigraphy is established from 3 5 khz seismic reflection data and a number of vibro cores across the narrow fehmarn belt between germany and denmark using detailed line drawings texture seismic and lithofacies analyses in a selected part of the study area a distinct depositional unit 5 was identified the unit was subdivided into sub units 5a to 5j due to a different seismic texture and facies pattern the base of the unit 5 is generally smooth but with step like parts which are interpreted to result from tectonism in each sub unit the seismic facies association includes mound oblique seismic facies and within channel deposits sigmoid shingled and parallel facies the sub unit represents offset stacked lagoonal and spit deposits deposited under conditions of progressive sea level rise sub units 5a to 5h show a change in depositional style from fluvial domination to gradually more wave influenced thus the dynamic evolution of the shallow marine sub sea floor environment and changes in depositional conditions are revealed by high resolution seismic facies associations

geochemistry and origin of the intrusive hosts of the noril sk talnakhcu ni pge sulfide deposits the world class deposits of cu ni and platinum group elements pge of the noril sk talnakh district in russia are hosted by relatively small complex mafic ultramafic bodies that intrude permian sedimentary rocks and the lowermost suites of the siberian continental flood volcanic sequence the noril sk type ore bearing intrusions immediately overlie and are probably penecontemporaneous with weakly mineralized intrusions of the lower talnakh type which have similar petrological features but contrasting and much more variable nd os and sr isotopic compositions several types of spatially associated intrusions were emplaced after the ore bearing intrusions and the flood volcanic sequence to clarify relations between the various types of igneous bodies flood volcanic rocks noril sk type intrusions lower talnakh type intrusions and later intrusions and to help understand the formation of the ore deposits we undertook a detailed geochemical and nd os and sr isotopic study of eight of the more important intrusions the data indicate that these intrusions formed by the input of a series of magma pulses each of which produced rocks with distinctive petrology and chemical compositions these compositions are interpreted to have formed from mixtures of mantle derived magmas and different types of crustal rock which were encountered and assimilated during passage to the surface some of these variations may be superimposed on heterogeneities inherited from the mantle source the magmas that formed the lower talnakh type intrusions became contaminated with large amounts of crustal rock in a deep staging chamber the chemical and isotopic characteristics of the resultant hybrid magmas are broadly similar to those of basalts of the lower and middle nadezhdinsky lava subsuites nd 1 2 which are located about one third of the way through the overlying lava sequence these magmas became saturated in sulfur during contamination and segregation of sulfides resulted in the depletion of chalcophile elements recorded in the nd 1 2 lavas magmas feeding the ore bearing intrusions had trace element and isotopic compositions similar to those of the basalts in the upper two thirds of the volcanic sequence these magmas underwent lower degrees of contamination in a deep staging chamber and sulfur saturation was not reached these magmas therefore contained a full compliment of chalcophile elements when they encountered anhydrite rich sediments during passage toward the surface assimilation of these sediments led to the segregation of sulfides to form the ores two aspects of our data impose important constraints on the ore forming process the first is the os isotopic composition of the ore sulfides avg os 7 which is similar to that of mantle rocks and very different from those of sulfides that segregate from highly contaminated magma the second is the absence of ni depletion in olivine in rocks from the ore bearing intrusions most notably in the ore rich picritic gabbrodolerites the simplest explanation is that the sulfides segregated from magmas that were not highly contaminated and were transported into the intrusions by magmas different from those that yielded the sulfide if this explanation is correct it imposes some modifications to earlier models of sulfide ore deposition in the conduits of flood basalts