a historical account of how continental drift and plate tectonics provided the framework for our current understanding of palaeogeographyg meinhold a m celâl şengorpalaeogeography continental drift and plate tectonics palaeogeography is the cartographic representation of the past distribution of geographic features such as deep oceans shallow seas lowlands rivers lakes and mountain belts on palinspastically restored plate tectonic base maps it is closely connected with plate tectonics which grew from an earlier theory of continental drift and is largely responsible for creating and structuring the earth s lithosphere today palaeogeography is an integral part of the earth sciences curriculum commonly with some exceptions only the most recent state of research is presented the historical aspects of how we actually came to the insights which we take for granted are rarely discussed if at all it is remarkable how much was already known about the changing face of the earth more than three centuries before the theory of plate tectonics despite the fact that most of our present analytical tools or our models were unavailable then here we aim to present a general conspectus from the dawn of palaeogeography in the 16th century onwards special emphasis is given to innovative ideas and scientific milestones supplemented by memorable anecdotes which helped to advance the theories of continental drift and plate tectonics and finally led to the establishment of palaeogeography as a recognized discipline of the earth sciences

arid zone groundwater recharge and salinisation processes an example from the lake eyre basin australia in arid central australia the 1 14 m km2 endorheic lake eyre basin leb experiences sporadic floods and contains saline shallow groundwater in this basin where on ground physical and chemical data are very sparse new observations of major ion chemistry stable isotopes 2h 18o 13c radiogenic isotopes 3h 14c and remote sensing modis data were used to investigate groundwater recharge and salinisation processes in 2006 2007 in january 2007 there was a large and intense local rainfall event followed by flooding to the normally dry lake eyre resulting from heavy rainfall in the northern leb that took 2 months to arrive at lake eyre groundwater chemistry from this study show no evidence of recharge from the floodwaters or the local rainfall however this does not preclude the process low transit times and low infiltrating volumes may mean that the recharge event has not yet been detected over the longer term the stable isotope chemistry indicates that groundwater is predominantly diffusely recharged during heavy local rainfall events 100 150 mm month and radiogenic isotopes reflect an older shallow groundwater efficiently mixing with recent decadal recharge the high total dissolved solids tds of regional shallow groundwater up to 52 5 g l is intrinsically linked with these recharge processes where infiltrating diffuse rainfall is evaporated and heavy rainfall events transport saline pore water saline due to evaporation in the unsaturated zone to the groundwater system the high tds of shallow groundwater beneath the dry lake eyre bed up to 322 g l is also controlled by evaporation however although evaporite minerals are prolific in the lake area the non conservative behaviour of br in pore water limits analysis of the role of halite mineral dissolution and precipitation reactions controlling groundwater salinity evaporation driven salinisation of shallow groundwater in arid central australia is distinct from the transpiration driven salinisation of groundwater in the australian murray basin located in a semi arid climate and results in relatively high groundwater salinity values compared with many other large arid zone endorheic basins across the world

intra and inter annual growth rate of modern stalagmites we measure the factors that determine growth rate temperature drip rate calcium ion concentration for 31 waters that feed stalagmites within six cave systems throughout europe water samples were collected at a frequency of at least 1 month to permit the modelling of both inter and intra annual growth rate variations utilising the theory of wolfgang dreybrodt chem geol 29 1980 89 105 chem geol 32 1981 237 245 dreybrodt w 1988 processes in karst systems springer verlag berlin 288 pp inter annual growth rates were measured using the stalagmites that were associated with the analysed water samples growth rate was determined from annual lamina counting specific time markers within the stalagmites and location of bomb 14c when compared to theoretically predicted values a good agreement between theoretical and measured stalagmite growth rates is observed r2 0 69 when compared to site climate and geochemical parameters a good correlation is observed between measured growth rate and mean annual temperature for five sites r2 0 63 and dripwater calcium content r2 0 61 but not drip rate r2 0 09 the good correlation with both calcium and temperature is due to soil co2 production being primarily determined by surface temperature and soil moisture however when we compare our data to that in the grotte de clamouse a site that has little soil cover we observe that the growth rate temperature relationship breaks down due to either the lack of soil co2 production or prior calcite precipitation intra annual data demonstrates that maximum growth rate occurs when calcium concentrations are high and that this occurs under different seasons depending on the hydrology of each site our results demonstrate a stronger dependence of intra annual stalagmite growth rate on dissolved calcium ion concentrations than drip rate for the range of drip rates investigated here 0 01 t 2drip s 1 but for lower drip rates this factor becomes important in controlling growth rate we suggest that for well monitored and understood sites stalagmite growth rate variations can provide useful information for palaeoclimate reconstruction

evaluation of salt sources and loads in the upland areas of the murray darling basin australia estimates of catchment salt balances throughout the murray darling basin mdb suggest mobilization of salt stores and generally increasing stream salinities it is widely assumed these salts are rainfall deposited cyclic salts of marine aerosol origin concentrated by evapotranspiration stored in groundwaters and mobilized by clearing of native vegetation in this paper the assumptions about the sources of salts in upland catchments in the south eastern region of the mdb are re evaluated the estimation of dissolved salts is re examined using electrical conductivity ec the assessment of stream salt loads from sporadic ec measurements and the sources of salts in upland catchments it is concluded that although evapotranspiration plays a significant role in the concentrations of salts in the lower mdb mineral weathering is a major contributor to stream salt loads in upland rivers of the mdb that supply over 80 of surface runoff to the murray river copyright 2009 john wiley sons ltd

a harbinger of plate tectonics a commentary on bullard everett and smith 1965 the fit of the continents around the atlantic in the 1960s geology was transformed by the paradigm of plate tectonics the 1965 paper of bullard everett and smith was a linking transition between the theories of continental drift and plate t

nickel isotopic variation in black shales from bohemia china canada and finland a reconnaissance study we present 60ni values for black shales determined by double spike mc icp ms the samples comprise paleoproterozoic talvivaara ni zn co cu black shales from finland neoproterozoic black shales from the tepla barrandian unit czech republic early cambrian ni mo rich black shales from the yangtze craton and devonian ni zn pge black shales from yukon canada in addition the sample set includes a black smoker sample from the logatchev hydrothermal field mid atlantic ridge the 60ni values vary from 0 84 0 09 to 0 62 0 04 2sd with a median of 0 10 n 28 ni isotopic compositions were predominantly lighter than those of abiotic terrestrial and extraterrestrial samples 0 15 and 0 27 mantle 0 23 gall et al 2017 present day seawater 1 44 cameron and vance 2014 dissolved ni from riverine input 0 84 cameron and vance 2014 ferromanganese crusts 0 9 2 5 gall et al 2013 devonian mississippian organic rich marine sediments lower jurassic organic rich marine sediments 0 2 2 5 average 0 92 n 18 porter et al 2014 and euxinic sediments of the black sea 0 14 0 51 vance et al 2016 however the range of 60ni values in our black shale samples was close to that of the weathering products of mafic ultramafic rocks ore and soil samples ranging from 0 60 to 0 30 ratie et al 2015 spivak birndorf et al 2018 ni sulfide ores hosted by archean komatiites from australia and canada 0 10 to 1 03 average 0 70 n 8 gueguen et al 2013 and archean ni rich magmatic sulfides from zimbabwe 0 28 to 0 47 n 6 hoffman et al 2014 based on our observations and considering the extremely low contribution of direct biological uptake of ni and a dominant ni residence in early fe ni sulfides we suggest that our mostly light ni isotopic compositions in metal rich black shales result from sulfidization of organic matter and ni removal into sulfides

reply to comment on chlorine 36 dating of very old groundwater 3 further results on the great artesian basin australia by t torgersen et al

trace elements in speleothems as recorders of environmental change speleothems are now established as important palaeoenvironmental archives and contain a number of suitable proxies although trace elements have been much less widely used than oxygen and carbon isotopes the complexity of the cave environment helps to explain this since the fluids from which speleothems form vary greatly in composition in space even within a cave chamber seasonally and over longer periods understanding the forcing factors for this variability is the key to decoding the significance of the trace element records a variety of techniques are available for trace element work and it is important to understand the strengths and limitations of each and also to seek an understanding e g by micro imaging techniques of whether the elements are associated with inclusions in the caco3 or are isolated within the crystal lattice for some elements there is a more or less predictable relationship between element ratios to ca in the water and in the calcite individual trace elements may be derived from atmospheric deposition superficial deposits or bedrock and can be recycled in soil processes before being transferred to the cave some components show an instantaneous response to water infiltration whereas others are only leached by slow flowing seepage waters changing in the proportion of water from fracture fed and seepage flow aquifer compartments is an important factor in influencing trace element supply high flows lead to higher fluxes of soil derived colloidally transported elements conversely under relatively dry conditions degassing of co2 results in prior calcite precipitation upflow of the site of speleothem deposition and leads to higher ratios of sr ca and mg ca some trace element variations in speleothems over time are induced during crystal growth whereby faster growth leads to a greater departure from equilibrium element partitioning despite the demonstrated temperature dependence of mg partitioning into calcite attempts at deriving palaeotemperature records from speleothems have been so far confounded by variations in solution mg ca and or crystallographic effects a number of case studies have effectively used trace elements such as speleothem mg as records of palaeo aridity using supporting arguments from modern monitoring or covariations with other parameters such as stable isotopes sr and u isotopes can also be indicators of palaeohydrology although sr isotope variations can also reflect varying aeolian input considerable progress has been made in decoding the meaning of annual trace element variations using criteria for understanding dripwater hydrology and ph this should lead in the future to more specific interpretations of how seasonality evolves through time

groundwater level fluctuation in the waimea plains new zealand changes in a coastal aquifer within the last 30 years data for the waimea plains new zealand indicate that the lower confined groundwater aquifer is hydraulically homogeneous and that shallow groundwater levels inland are affected mostly by anthropogenic processes while those near the coast are affected more by sea level variation analysis of long term data for new zealand indicates that sea level has increased continuously but trends are not spatially uniform results from non parametric trend analysis show that rising trends for groundwater levels are predominant in the shallow aquifer both inland on the waimea plains and for recent years near the coast while decreasing trends are evident in the underlying confined aquifer near the coast groundwater level change in the shallow aquifer appears to be more affected by climate change than the lower confined aquifer correlation analysis indicated that groundwater levels are more affected by rainfall during the rainy season than the dry season and more influenced by rainfall inland than near the coast groundwater level declines in the lower confined aquifer near the coast which has its major recharge area inland in the catchment may be substantially affected by groundwater abstraction in inland areas as well as sea level variation but there are little evidences of seawater intrusion meanwhile groundwater recharge over the catchment area has great influence on rising groundwater levels in the shallow aquifer and its recharge is estimated to be 417 8 mm year using chloride concentrations of precipitation and groundwater

pb zn sedex deposits and their copper stockwork roots western cuba base metal deposits in western cuba belong to the sedex type as defined by carne and cathro 1982 the age of the mineralisation is jurassic the host rocks of the deposits are gritstones sandstones and black shales with no igneous rocks involved sulphur isotopic data from pyrite and chalcopyrite indicate a biogenic and magmatic origin at least for part of the cuban sulphides the inferred tectonic setting of these deposits is that of a passive continental margin the pb zn cu mineralisation in cuba is hosted in the siliciclastic sedimentary rocks of the san cayetano formation lower upper jurassic in age which indicates derivation of quartzose grains from recycled orogen source areas related to either the grenville or pan african granitic metamorphic belts

timing and dynamics of the last deglaciation from european and north african δ13c stalagmite profiles comparison with chinese and south hemisphere stalagmites abstract the last deglaciation and its climatic events such as the bolling allerod ba and the younger dryas yd have been clearly recorded in the 13 c profiles of three stalagmites from caves from southern france to northern tunisia the three 13 c records dated by thermal ionization mass spectrometric uranium thorium method tims show great synchroneity and similarity in shape with the chinese cave 18 o records and with the marine tropical records leading to the hypothesis of an in phase between 15 5 and 16 ka 0 5 ka postglacial warming in the northern hemisphere up to at least 45 n the ba transition appears more gradual in the speleothem records than in the greenland records and the allerod seems warmer than the bolling showing here close similarities with other marine and continental archives a north south gradient is observed in the ba trend it cools in greenland and warms in our speleothem records several climatic events are clearly recognizable a cooler period at about 14 ka older dryas od the intra allerod cold period at about 13 3 ka the yd cooling onset between 12 7 and 12 9 0 3 ka similar to the ba the yd displays a gradual climate amelioration just after its onset at 12 75 0 25 ka up to the preboreal and is punctuated by a short climatic event at 12 15 ka even though the southern hemisphere stalagmite records seem to indicate that the postglacial warming started about 3 ka 1 8 ka earlier in new zealand 41 s and about 1 to 2 ka earlier in south africa 24 1 s large age uncertainties essentially due to slow growth rates make the comparison still perilous the overall 13 c speleothem record seems to follow a baseline temperature increase controlled by the increase in insolation and punctuated by cold events possibly due to the n america freshwater lake discharges

plate tectonics and orogenic research after 25 years a tethyan perspective abstract orogeny the process by which the earth s prominent mountain ranges are constructed has been a central topic of interest in the earth sciences since at least the end of the 18th century the recognition that strains and displacements of very considerable magnitude occur along all of the three dimensions within an orogenic belt during its evolution has grown gradually during the last two centuries emphasis on primary vertical movements dominated the ideas on the nature of orogeny during the first half of the 19th century whereas compression and consequent uplift across mountain belts were believed to be the main cause for their origin during the subsequent one hundred years or so that were spent under the dominance of the fixist contraction theory mobilist tectonicians realised that continental drift in places also required motion along the trend of orogenic belts but this view did not gain general acceptance recognition of significant strike slip motion parallel or subparallel with mountain ranges evolved independently and mostly within the fixist camp by the 1960 s presence of important motions both along and across mountain belts had become common knowledge but no theoretical basis existed to account for them all

effects of glaciations upon karst aquifers in canada abstract in canada there are 5 7 10 5 km 2 of limestone and marble outcrop 6 10 5 km 2 of dolomite and 8 10 4 km 2 of sulfate rocks in addition halite subscrops beneath 5 10 5 km 2 of the central prairie region and interacts with modern groundwater circulation to a varying extent more than 90 of the total outcrop subcrop has been repeatedly glaciated the most recent glaciation late wisconsin terminated 13 000 5000 yrs b p in different areas carbonate terrains still partly buried by glacier ice may be inspected in the rocky mountains nine distinct effects of glacial action upon the propagation and efficiency of karst aquifers are recognized destructive effects include erasure dissection infilling and injection bedrock solution may be inhibited during non glacial periods by a cover of glacial drift rich in carbonate clasts glacial burial may also preserve an aquifer and enhance its storage characteristics aquifer expansion may be stimulated by raising the hydrostatic head or steepening hydraulic gradients or by crustal flexure during deglacial isostatic rebound the differing effects make general prediction of the state of an aquifer in glaciated terrains difficult

testing theoretically predicted stalagmite growth rate with recent annually laminated samples implications for past stalagmite deposition annually laminated stalagmites deposited over the last 30 160 years are analysed to determine their growth rate three natural and artificial cave sites in england france and belgium were chosen for their wide range of variability in growth rate determining variables and multiple samples were taken from each site the annual nature of laminae deposition within the stalagmite calcite was confirmed by comparison to the date of cave void opening 14c analyses or by using dated event horizons measured stalagmite growth rate was determined from annual laminae thickness measurements and compared to that theoretically predicted from the chemical kinetics of the calcite precipitation reaction a good agreement is observed between empirical observations and theoretical predictions although two complicating factors variations in calcite porosity and seasonal cessation of the water supply to the samples both affect the growth rate implications for the extraction of palaeoclimate information from stalagmite growth rate are discussed

geochemistry of ground waters from the great artesian basin australia herczeg a l torgersen t chivas a r and habermehl m a 1991 geochemistry of ground waters from the great artesian basin australia j hydrol 126 225 245 ground waters from the confined lower cretaceous jurassic aquifer of the great artesian basin australia gab are characterised by na hco 3 type waters throughout the eastern and central parts of the basin and na sq c1 type waters in the western part sodium and bicarbonate increase in concentration from the northeastern margins to the southwestern discharge areas along the regional groundwater flowlines a mass balance and equilibrium model for major dissolved species and stable carbon isotopes of dissolved inorganic carbon show that the chemical trends observed are caused by mass transfer reactions involving cation exchange of na for ca mg carbonate dissolution and reactions between na and kaolinite to form na smectite the stable carbon isotopic composition of dissolved inorganic carbon dic increases from values of about 15 o near the basin margins to 6 o in the interior of the basin an inverse relationship exists between 6 3c and dic indicating addition of enriched carbon as the ground waters move basinwards a t2c 3c mass balance indicates that the trend toward heavier 6 3c values in the interior of the basin results from bacterial reduction of carbon dioxide to produce methane rather than dissolution of and equilibration with carbonate minerals the gab aquifer system is apparently open to co which is the product of in situ anaerobic fermentation producing co 2 enriched in t3c the chemical evolution of the major dissolved species and carbon isotope distribution in the eastern and central parts of the gab can then be envisaged as an initial pco 2 up to several orders of magnitude above atmospheric level is acquired within the recharge area by plant respiration and oxidation of organic matter in the soil zone initially silicate and carbonate minerals may dissolve at least in some parts of the basin resulting in increased alkalinity higher ca and mg concentrations and a 6 3c concentration of the dic of around 12 0 processes such as cation exchange of na for ca and mg in addition to the removal of some na by reverse weathering which produces a na smectite dominate in the interior of the gab the chemistry of ground waters derived from the western recharge areas is controlled by evaporite dissolution as indicated by very high ci br ratios

understanding the salinisation process for groundwater in an area of south eastern australia using hydrochemical and isotopic evidence abstract increases in groundwater salinity down gradient are a common occurrence in catchments throughout australia exacerbating the effects of dryland salinisation in discharge areas groundwater hydrochemical and isotopic data from the willaura catchment in south eastern australia which is affected by both primary natural and secondary human induced salinity allowed the factors that cause the down gradient trend in salinisation within this catchment to be determined the overall salinity of the groundwater 0 8 70 ms cm is controlled by evapotranspiration which concentrates cyclic salts in the unsaturated zone greatly increasing the salinity of the soil water to 3700 6400 mg l cl the progressive addition of this saline soil water to fresher groundwaters recharged on the catchment margins causes a gradual increase in salinity down gradient the groundwater stable isotope compositions show that most recharge occurs in winter and spring groundwater salinities increase around the saline lakes of the discharge zone due to direct evaporation from shallow watertables and minor dissolution of halite as indicated by cl br ratios mineral water interactions within the aquifers cause a slight overall reduction in salinity conversion of kaolinite to smectite and illite and cation exchange of na for ca2 on smectites cause na cl mg2 cl k cl si cl and hco3 cl ratios to progressively decline and ph to gradually increase down gradient oxidation of organic matter causes a strong decrease in the redox potential of the groundwaters down gradient the groundwater ages increase from modern containing tritium on the catchment margins to 8000 years based on 14c dating at the end of the 25 km flow path the older groundwaters are isotopically heavier than the younger waters probably due to recharge during a wetter climate in the early holocene the groundwater ages show clearly that the progressive addition of saline soil water causing groundwaters to become more saline down gradient has occurred throughout the holocene and may explain the occurrence of primary salinisation within many australian catchments

hydrogeochemistry of the chiang mai basin northernthailand abstract chemical composition of groundwater samples collected from 247 boreholes throughout the chiang mai basin was determined in order to describe the background ion concentrations and to identify the major hydrogeochemical processes that control the observed water chemistry the investigation results indicate that the groundwater is generally free from heavy metals although exceptionally high fe mn f and na are found locally the groundwater of the chiang mai basin has evolved chemically through water rock interactions from low tdi and low ph meteoric water recharges principally at basin rims towards higher tdi and ph groundwaters discharges mainly along the through flowing mae ping river the average groundwater has hydrochernical facies either of ca na or na ca bicarbonate type with neutral ph and total dissolved ions tdi of about 10 meq 1

the geometry of continental displacement and its application to arctic geology eugen wegmann s early approaches published in the geologische rundschau in 1943 plate tectonics developed around 1965 as a powerful tool to describe the tectonic movements of the earth s crust the article demonstrates that basically four already existing theoretical concepts subduction seafloor spreading the application of euler s theorem and transform faults had to be combined to arrive at the modern theory alfred wegener father of the theory of continental displacement is often credited as the most direct forerunner of plate tectonics however none of the aforementioned concepts had been developed by him the present article deals with the hitherto not duly credited contributions of the swiss geologist eugen wegmann 1896 1982 he developed in a series of highly original papers published between 1943 and 1948 one of them in the geologische rundschau a critical test of the theory of continental displacement based on the regional geology of the arctic furthermore he gave a very concise account on the geometrical principles of drift movements as a result he developed for the first time 25 years before mckenzie and parker s nature 216 1276 1280 landmark paper on the pacific 1967 the geometrical basis to graphically test plate motion directions however his work has not yet received the credit it deserves neither by scientist nor by historians of science

stable isotope geochemistry of cold co2 bearing mineral spring waters daylesford victoria australia sources of gas and water and links with waning volcanism abstract mineral springs in the victorian central highlands australia have high co 2 contents and naturally effervesce 13 c values of co 2 gas and dissolved inorganic carbon are 10 6 to 7 0 and 5 9 to 0 1 respectively with a net 13 c of 8 to 3 the carbon in these waters was derived from a mantle source associated with local pliocene to recent basaltic newer volcanic province rocks previously reported 3 he 4 he 1 2 3 1 relative to air and high he ne ratios are also consistent with the presence of magmatic volatiles silica contents imply that the waters were never heated above 130 c and that the system is not hydrothermal the occurrence of carbonated mineral springs in a relatively small region of the newer volcanics province where volcanic activity ceased several thousands of years ago may be due to the presence of late intrusions combined with deep circulation of water through deeply weathered and fractured ordovician basement a region of low seismic velocity under the daylesford area potentially images those intrusions most spring waters have 18 o and 2 h values of 8 to 6 and 45 to 35 respectively and lie to the left of the local and global meteoric water lines the anomalously low 18 o values results from co 2 exsolution at low temperatures which strongly partitions 18 o into the gas the lack of waters lying to the right of the local meteoric water line also implies that water rock interaction at elevated temperatures did not occur the 2 h values are lower than contemporary meteoric water suggesting that the waters may have recharged under colder climate conditions several thousand years ago the local ordovician rocks are gold bearing the present spring system is cold and would not efficiently transport au however volcanic is waning and the spring systems at the time of volcanism may have been hotter and able to redistribute au

a pioneer of precambrian geology boris choubert s fit of the continents across the atlantic 1935 and his insights into the proterozoic tectonic structure of the west african craton and adjacent areas abstract plate tectonics revolutionized the earth sciences during the 1960s and led to a fundamentally new view of tectonic processes inside mountain belts application of the new theory to pre permian and especially precambrian orogenic belts developed somewhat reluctantly during the 1970s and 1980s the present article presents and discusses the ideas of boris choubert 1906 1983 a french colonial geologist of russian origin which he first developed in 1935 he tried to test wegener s theory of continental displacement a forerunner of plate tectonics by applying it to paleozoic and precambrian orogenic belts around the atlantic a topic altogether neglected by wegener to achieve this he produced a fit of the continents across the atlantic which is almost identical to the famous 1965 fit of bullard et al starting from this paleozoic continental configuration he presented an inter continental synthesis of precambrian geology and discussed problems from a wide array of topics ranging from regional tectonics of the west african craton questionable precambrian fossils tillites and cap carbonates to the supposed origin of detrital diamonds in gabon and brazil he also provided probably the first precambrian plate reconstruction avant la lettre after his 1935 paper choubert worked for decades in africa and south america and had opportunity to test and refine his synthesis his example is a call addressed to present day geologists working on precambrian geology in africa and other regions to consult the old colonial literature which contains a wealth of factual information and theoretical inspiration which is still of interest today

bacterial metabolism and the δ13c composition of ground water floridan aquifer system south carolina viable bacteria are present 10 5 10 7 cells per gram sediment in the clastic water table and hawthorn aquifers that overlie and recharge the floridan aquifer near hilton head island south carolina incubation of cored sediments shows that indigenous bacteria are capable of producing carbon dioxide co 2 as they metabolize sedimentary organic material estimated in situ co 2 production rates based on dissolved inorganic carbon dic changes and ground water flow rates are in the range of 10 2 mmol l 1 yr 1 two independent lines of evidence 1 isotope balance calculations on dic along ground water flow paths and 2 direct measurement of the isotopic composition of co 2 produced by incubation of hawthorn sediment suggest that bacterially produced co 2 in the hawthorn aquifer is much heavier isotopically 13 c 10 to 15 than associated sedimentary organic material 13 c 21 the relatively heavy 13 c values of dic in water from the floridan aquifer which receives much of its recharge from the overlying hawthorn reflect this source of isotopically heavy co 2

base metal rich metamorphosed black shales associated with proterozoic ophiolites in the kainuu schist belt finland a genetic link with the outokumpu rock assemblage metamorphosed black shale is an essential component of the early proterozoic outokumpu rock assemblage together with serpentinite calc silicate rock and quartz rock this rock assemblage hosting the major cu co zn deposits of outokumpu and considered ophiolitic in origin has also been encountered to the northwest in the kainuu schist belt the rift basin encompassing the two areas was intruded by ophiolite complexes 1 96 1 97 billion years ago remnants of ultramafites are met as serpentinite and talc carbonate rock lenses bounded by faults along the western margin of the kainuu schist belt the black schist formations range in thickness from tens of metres to 400 m metal rich layers occur close to the serpentinite bodies the most extensive formations of metal rich black schist 300 mt 0 26 ni 0 14 cu 0 53 zn have been encountered at talvivaara the lithological mineralogical and geochemical results indicate a genetic link between the jormua talvivaara alanen and pappilanmaki prospects in the kainuu schist belt and the outokumpu rock assemblage

effects of glaciations and permafrost upon the development of karst in canada canadian examples suggest that karst landforms may be divided into eight types in terms of their temporal relationships to the record of repeated quaternary glaciations two types are postglacial two are subglacial one type occurs where glacial features are adapted to karstic drainage and three types display sequences of karstic and glacial action glacier effects upon karst landforms and their underlying aquifers display the gamut of possibilities they may destroy inhibit preserve or stimulate karst development where continuous permafrost is maintained when covered by glacier ice postglacial karst is limited to the active layer epikarst where permafrost is thawed beneath ice or during deglaciation there are a variety of postglacial karst developments depending in part upon climate and in part upon local lithologic and relief conditions

anoxic sediments an important environment for pge an overview anoxic sediments and metasediments have been recently recognized as important host environments for the platinum group elements pge economically significant pge concentrations have been reported from marine metal rich black shales in china yukon canada and poland these ore bearing horizons are characterized by extremely restricted vertical and sometimes larger horizontal extents they are associated with the evolution of intracontinental rifting structures without any magmatic activity suggesting a possible driving mechanism for mineralization processes complex pge associations including a significant relationship of pd and pt with ni bi se y and also with sb cu co au u and f are suggested using the results of a new statistical evaluation of available geochemical data these occurrences show more common features with other hydrothermal pge deposits the rift volcanic related marine metal rich black shales of the czech republic and finland however display lower pge values the mineralized layers are much thicker with a typically limited horizontal extent showing a close association with volcanic centres pd reveals a strong correlation with ni zn au and v pt exhibits a highly significant link with the cu and mo phases low average nicu ratios and pge au chondrite normalized patterns are similar to those of some magmatic pge deposits hosted in mafic and ultramafic rocks it is very likely that organic matter played an important role in the genesis of pge accumulations in metal rich black shales in both rift and rift volcanic related environments

geochemistry of archean carbonaceous cherts deposited at immature island arc setting in the pilbara block western australia abstract archean carbonaceous meta cherts upper greenschist to amphibolite facies from the nickol well unit the cleaverville group 3 2ga in the roebourne district in west pilbara are characterized by variable al2o3 tio2 zr tio2 and cr th values and by high concentrations of carbon and some trace metals distribution patterns of the cherts on a newly proposed diagram al2o3 tio2 element al2o3 indicate that concentrations of cr v and ni can be explained by contributions of clastic components whereas concentrations of cu zn and pb are much higher than those expected solely from clastic contributions detrital material in the cherts was derived from a wide variety of volcanic sources mafic ultramafic felsic sources consistent with the inferred geological setting of the cleaverville group immature island arc setting excess cu zn and pb are probably from hydrothermal solutions as suggested by positive eu anomalies and enrichment in heavy rare earth elements ree in chondrite normalized patterns high concentrations and light isotopic values of c 17 to 24 per mil in the cherts indicate that the precursory sediments were enriched in organic materials although it is unclear whether the organic material was derived from organic particles that settled from the ocean surface or benthic microbes in either case it is possible that this material played an important role in the accumulation of heavy metals cu zn and pb in the sediments

application of stable carbon isotopes to early biochemical evolution on earth the emergence and early evolution of life on earth have long been intriguing subjects for scientific inquiry and a continuous source of intel lectual excitement current work at this frontier proceeds along a number of different avenues and comprises a variety of disciplinary approaches that together strongly suggest that the earth was inhabited by life as early as almost 4 gyr ago the present state of the field as inferred from the results of a broad interdisciplinary approach has recently been summarized by j w schopf and coworkers cf schopf 1 983 it is with the advantage of such a synoptic view that the present review addresses a single facet of the theme namely the potential isotopic infer ences of the presence of co2 fixing autotrophic organisms for the carbon cycle of the early earth with biologically derived organic carbon as well as carbonates limestone dolomite etc abundantly preserved in sediments relevant isotopic evidence should have been encoded in the geologic record from its onset about 3 8 gyr ago it has been known since the pioneering studies by nier gulbransen 1939 murphey nier 1941 and rankama 1948 that the trans formation of inorganic carbon into living matter entails a marked bias in favor of the light isotope c2c with the heavy species l3c retained in the inorganic reservoir subsequent work performed by many investigators e g craig 1953 park epstein 1960 has confirmed that all common

secular distribution of highly metalliferous black shales corresponds with peaks in past atmosphere oxygenation highly metalliferous black shales hmbs are enriched in organic carbon and a suite of metals including ni se mo ag au zn cu pb v as sb se p cr and u pge compared to common black shales and are distributed at particular times through earth history they constitute an important future source of metals hmbs are relatively thin units within thicker packages of regionally extensive continental margin or intra continental marine shales that are rich in organic matter and bio essential trace elements accumulation and preservation of black shales and the metals contained within them usually require low oxygen or euxinic bottom waters however whole rock redox proxies particularly mo suggest that hmbs may have formed during periods of elevated atmosphere po2 this interpretation is supported by high levels of nutrient trace elements within these rocks and secular patterns of se and se co ratios in sedimentary pyrite through earth history with peaks occurring in the middle paleoproterozoic early cambrian to early ordovician middle devonian middle to late carboniferous middle permian and middle to late cretaceous all corresponding with time periods of hmbs deposition this counter intuitive relationship of strongly anoxic to euxinic localized seafloor conditions forming under an atmosphere of peak oxygen concentrations is proposed as key to the genesis of hmbs the secular peaks and shoulders of enriched se in sedimentary pyrite through time correlate with periods of tectonic plate collision which resulted in high nutrient supply to the oceans and consequently maximum productivity accompanying severe drawdown into seafloor muds of c s p and nutrient trace metals the focused burial of c and s over extensive areas of the seafloor during these anoxic to euxinic periods likely resulted in an o2 increase in the atmosphere causing short lived peaks in po2 that coincide with the deposition of hmbs as metals become scarce particularly mo ni se ag and u the geological times of these narrow hmbs horizons will become a future focus for exploration

soil carbon dioxide and weathering potentials in tropical karst terrain peninsular malaysia a preliminary model co2 concentrations at depths of 15 30 and 50 cm were determined over a one year period in six karst soils in the malay peninsula evidence suggests that the highest single co2 value maxco2 per cent recorded at each site depth provides the best estimate of conditions during groundwater recharge events soil depth cm and bulk density bden are the best predictors of maxco2 with the equation loglo maxco2 1 146 bden 0 00698 depth 1 227 accounting for 86 per cent of the variation this equation is used to model maxco2 at seven more remote sites soil throughflow patterns and groundwater recharge points are estimated from slope pantometer and soil depth surveys in order to assess the co2 concentration with which soil waters ultimately equilibrate before entering the limestone limestone weathering seems to be predominantly of the open system type the overall mean maxco2 of 1 65 per cent corresponding with a weathering potential of 167 ppm caco3 weathering potentials vary markedly ranging from 62 82 ppm on rocky hilltops to more than 280 ppm on certain tower karst footslopes in selangor and the kinta valley and on moderate hillslopes developed in impure limestones in the boundary range

the occurrence and origin of methane in some groundwater flow systems the origin of methane in selected groundwater flow systems is investigated through carbon isotope geochemical studies combined with hydrogeological and hydrogeochemical information methane is a common trace constituent in these groundwaters and occasionally constitutes a major carbon pool two modes of origin for methane are commonly recognized microbial production biogenic methane and non biological chemical production thermocatalytic methane in the groundwaters sampled the few thermocatalytic methanes encountered have 13c values greater than about 45 whereas the more common normal biogenic methanes have 13c values less than about 60 biogenic methanes from sanitary landfill sites have intermediate 13c values of about 38 to 56 and so can easily be distinguished from normal biogenic methane the carbon source for biogenic methane is usually organic matter present in the aquifer materials the carbon isotope ratios of dissolved methane and total inorganic carbon in sampled groundwaters ar

the carbonate system geochemistry of shallow groundwater surface water systems in temperate glaciated watersheds michigan usa significance of open system dolomite weathering we present here a field geochemical study of controls on carbonate weathering within rapidly circulating shallow groundwater surface water systems in the glaciated mid continent region groundwaters and surface waters in three watersheds spanning the upper to lower peninsulas of michigan consist of ca 2 mg 2 hco 3 solutions derived from the open system dissolution of calcite and dolomite in soils developed on mixed mineralogy glacial drift the thermodynamic stabilities of calcite and dolomite both decrease with decreasing temperature with dolomite more strongly affected thus the low mean annual temperature of these temperate weathering environments maximizes the absolute solubility of dolomite as well as its solubility relative to calcite many groundwaters in the study area approach equilibrium with respect to the more soluble dolomite and are moderately supersaturated with respect to calcite groundwaters in each watershed have distinct and relatively narrow ranges of carbon dioxide partial pressure p co 2 values which increase significantly from north to south log p co 2 of 3 0 to 2 2 atm suggesting that there are landscape level differences in carbon transformation rates in soil weathering zones increases in weathering zone p co 2 values produce hco 3 concentrations that vary by a factor of five but the mg 2 ca 2 and mg 2 hco 3 ratios of all groundwaters are similar suggesting relatively constant weathering input ratios of calcite and dolomite although surface waters commonly are between 2 and 10 times supersaturated with respect to calcite the mg 2 hco 3 ratios of surface waters are very close to initial groundwater values suggesting that back precipitation of calcite is not a significant process in these systems the enhanced solubility of dolomite at low temperatures coupled with the landscape level differences in carbon cycling suggest that temperate zone weathering reactions in glaciated terrains are significant contributors to continent scale fluxes of both mg 2 and hco 3

environmental impact of mineralised black shales abstract black shales are sedimentary rocks containing 0 5 of organic carbon they host polymetallic deposits which have been mined for cu ni zn mn p mo v u au and pge platinum group elements even sub economic occurrences provide potential risk of acid rock drainage when exposed to oxic surface environment the natural acid neutralisation potential varies depending on the adjacent rock units especially on the presence of calcareous rocks the chemical and mineralogical composition of black shale is reflected in the quality of the surface waters and groundwater cu ni pb u and zn are recognised as major pollutants though the environmental impact is characteristically polymetallic just like the black shale occurrences hence the environmental impacts have to be evaluated in each occurrence the proterozoic ni zn cu co deposit at talvivaara finland is reviewed in more detail as an example of a large low grade deposit that is currently exploited with open pit mining and a bioleaching process together with the proterozoic central african copperbelt the cambrian u mo deposits in sweden the cambrian ni mo pge deposits in china and the cambrian ordovician u deposits in south korea the devonian ni zn pge occurrences in yukon canada and kentucky usa and the permian cu ag deposits in poland and germany the mineralised horizons may be merely few centimetres thick like in yukon or hundreds of metres thick like at talvivaara both natural and anthropogenic environmental impacts of black shales are reviewed world wide and based on the overview of the state of the art an integrated research approach is suggested for the comprehensive assessment of the risk black shales are natural sources of soil and water contamination at talvivaara the geochemical background includes higher than average concentrations of ni cu zn and mn in glacial till peat surface waters and groundwater as well as in stream and lake sediments bioaccumulation by plants has been reported in china and korea even endemic diseases have been proposed to be linked with the contamination derived from the weathering and leaching of harmful elements from black shale anthropogenic actions exposing the black shale bedrock and associated soils to oxic conditions further intensifies acid rock drainage regional or nation wide mapping of the black shales is recommended to detect potential risk areas finland has recently completed the country wide mapping program of black shales with airborne geophysics integrated with geological petrophysical and geochemical studies the black shale database is actively used in regional planning and by environmental authorities research institutes and consulting companies in the case of the historical black shale mining areas like in the kupferschiefer in germany restoration measures have been applied to prevent further acid mine drainage in active and future mining projects a comprehensive environmental impact assessment with effective monitoring programmes and closure plans play a crucial role in the prevention of acid mine drainage from the black shale associated deposits

chlorine 36 dating of very old groundwater 1 the great artesian basin australia chlorine 36 has many advantages as a dating tool for very old groundwater these advantages include a suitable half life 3 01 x 10 sup 5 years simple geochemistry conservative behavior in groundwater and a general absence of subsurface sources at levels comparable to the atmospheric input recent advances in tandem accelerator mass spectrometry have permitted the analysis of sup 36 cl at low abundance expected following residence in the subsurface for 10 sup 6 years or more in order to test the suitability of sup 36 cl for dating very old groundwater the sup 36 cl cl ratios of 26 groundwater samples from the great artesian basin of australia have been measured groundwater ages calculated from the sup 36 cl data compare favorably with ages computed independently from hydrodynamic simulations

the origin of diamonds in western minas gerais brazil important diamond mineralized alluvium colluvium occurs in western minas gerais wmg in the brasilia orogenic belt 700 450 my diamonds are geographically related to glacial and periglacial sediments upper proterozoic and permo carboniferous wadi and debris flow conglomerates lower cretaceous and upper cretaceous and ultramafic alkaline rocks intrusive and extrusive including kimberlites leucitites kamafugites carbonatites etc of cretaceous age petrological data indicate that the rocks originally petrographically classified as kimberlites present mineralogical chemical and isotopical differences with group i and ii kimberlites and more closely resemble kamafugites the brasilia orogenic belt presents features of a wilson cycle implying that wmg does not fulfil the geotectonic and geothermometric requisites to host primary diamond sources an analysis of field relations and sedimentology in wmg shows that the majority of the diamonds have been transported by glacial events from the sao francisco craton further east

an early proterozoic ophiolite the jormua mafic ultramafic complex northeastern finland abstract the 1 96 ga old jormua complex comprises a fault bounded unit 2 5 20 km in the centre of the kainuu schist belt at the eastern margin of the early proterozoic svecokarelides the complex was dismembered and metamorphosed to lower amphibolite facies during the svecokarelian orogeny in the intact complex the basal unit was formed by serpentinites the middle unit of mafic dykes and the uppermost extrusive unit of basaltic pillow lavas gabbroic rocks are present as intrusive bodies in the serpentinites and narrow interdyke screens within the dyke unit trondhjemitic rocks occur as minor segregations in the gabbroic rocks or as cross cutting narrow dykes in the mafic dyke unit the dyke unit is locally composed exclusively of subparallel metabasalt and metadolerite dykes in places interdyke metagabbro and serpentinite screens are abundant well preserved chilled margins are common and many dykes are split and intruded by younger dykes the chemical composition of the serpentinites indicates derivation from harzburgitic dunitic mantle peridotites the gabbroic rocks which represent obvious tholeiitic cumulates show extreme differentiation similar to gabbros of the high ti ophiolites and gabbros dredged from present midocean ridges in chemistry the trondhjemitic rocks are close to granitic rocks from mid ocean ridges and high ti ophiolites the similar chemical composition of the dykes and lavas of the complex indicates that they are cogenetic both being tholeiitic metabasalts with chondrite normalized ree patterns ranging from slightly lree depleted to slightly lree enriched ones compared with modern rocks the jormua metabasalts most closely resemble transitional midocean ridge basalts it is suggested that the jormua complex and related mafic ultramafic bodies in eastern finland originated as divergent margin ophiolites concomitantly with the break up of the archaean craton in the extensional stage of the svecokarelian orogeny which culminated in the opening of a major ocean after 1 97 ga the tectonic emplacement of these ophiolites into their present locations occurred in connection with thrusting during the compressional stage of the orogeny about 1 9 ga ago

geochemical evidence for the hydrothermal origin of sulphur base metals and gold in proterozoic metamorphosed black shales kainuu and outokumpu areas finland metamorphosed black shale formations 120 150 m thick with median concentrations of 7 non carbonate carbon and 6 8 sulphur are abundantly met in drill cores in the kainuu and outokumpu areas carbon isotope 3c values are comparable to the average isotopic composition of non carbonate carbon in sedimentary rocks the rare earth element patterns show cerium depletion indicating a marine origin base metal concentrations in black shales are high in the talvivaara mineralization ore estimate 300 mt with 0 26 ni 0 14 cu and 0 53 zn and in the vicinity of ophiolite complexes in the kainuu schist belt the median value for gold is 35 ppb max 170 ppb in the western part and 16 ppb max 180 ppb in the east highest platinum and palladium concentrations encountered are 60 70 ppb it is shown that in the kainuu black shales concentrations of sulphur base metals and precious metals have been increased by hydrothermal processes as indicated by positive europium anomalies elevated mercury concentrations max 7 5 ppm high sulphur isotope 34s values and the enrichment of sulphur and base metals relative to carbon the processes operative during the deposition of these shales find an analogy in recent processes in ocean ridge spreading axes

geomorphic inheritance and the development of tower karst four genetic types of tower karst are identified the most typical consisting of residual hills protruding from a planed carbonate surface veneered by alluvium two extreme possibilities for tower karst evolution are recognized a direct development that is independent of any previous morphology and a sequential development that depends explicitly on the morphological characteristics of a previous cockpit karst phase examples of both are described although the latter appears the more common south china tower karst is examined in this light palaeomagnetic analysis of cave deposits in a tower near guilin indicate the feature to be a time transgressive landform four principal controls of tower development are discussed and a model of tower evolution is presented

the effects of geomorphology and seasonality on the chemistry of carbonate groundwater abstract the equilibrium chemistry of carbonate groundwater at the regional and long term scales of aggregation is affected by geomorphic factors and by the seasonality of temperature and recharge regimes the general trend of ca concentration differences between regions is governed by annual mean air or groundwater temperature and by the nature of the solution system higher concentrations result from the coincident system where carbonate material soil air and water are all present together and lower concentrations from the sequential system where carbonate material occurs downstream of the soil air coincident systems occur in areas where carbonate material is present in the regolith either by natural or human activity where a porous or friable bedrock lies at shallow depth or where soils are shallow sequential systems occur where there is a deep non carbonate regolith where there is a non carbonate cap to the carbonate bedrock or where there is a high water table reductions in equilibrium ca concentration can be caused by low soil air volumes relative to percolation volume this may be particularly significant in cool regions where soils are shallow and clayey and where recharge occurs in short high intensity events

bacterial production of methane and its influence on ground water chemistry in east central texas aquifers geochemical and isotopic data for methane and ground water indicate that gaseous hydrocarbons in eocene aquifers in east central texas form by bacterial processes the 13c values of methane from five wells in the clay rich yegua and cook mountain formations range from 71 to 62 methane from ten wells in the cleaner sands of the sparta and queen city formations have 13c values between 57 and 53 the carbon isotopic difference between methanes from the yegua and sparta aquifers is comparable to the isotopic difference in sedimentary organic matter from outcrops of the units suggesting substrate control on the 13c of bacterial methane hydrogen isotopic compositions of methane from the aquifers are similar averaging 181 this high value suggests methane production predominantly by co2 reduction the 13c of dissolved inorganic carbon dic in high bicarbonate waters increases from about 20 to 0 with increasing dic mass balance calculations indicate that the dic added to the ground water has 13c values as high as 10 this 13c enriched carbon is predominantly derived from co2 production by fermentation and anaerobic oxidation reactions combined with co2 consumption by co2 reduction this process is responsible for high bicarbonate contents in these and probably other gulf coast ground waters

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

pyrite and organic matter in phanerozoic normal marine shales data have been obtained from our own chemical analyses and from the literature for the concentrations of organic carbon c and pyrite sulfur s in over 600 samples of cambrian to recent normal marine shales normal marine refers to deposition in oxygenated bottom water as evidenced by the presence of benthic fossils and or indicators of bioturbation all samples were selected to minimize 1 1 loss of c and or s due to weathering at the outcrop by emphasizing the use of drill core material 2 2 analytical errors and non diagenetic effects by avoiding sediments low in c or s content such as sandstones 3 3 fe limitation of pyrite formation by avoiding limestones cherts and euxinic shales 4 4 metamorphic loss of c relative to s by avoiding rocks obviously subjected to even low grade metamorphism our results indicate that 1 there is generally a good positive linear correlation between organic c and pyrite s for normal marine shales of all ages and 2 the mean cs ratio for normal marine shales has varied over time devonian to tertiary shales exhibit mean cs weight ratios 1 8 0 5 somewhat lower than quaternary sediments meancs 2 8 this we believe is due to preferential c loss relative to s during biogenic methanogenesis plus diagenetic heating distinctly lower mean c s values for the cambrian and ordovician 0 5 0 1 cannot be explained solely in terms of diagenetic c loss and instead must represent low original ratios the low original ratios we suggest were due mainly to the absence of bacterially refractory organic matter added to the marine environment by rivers at that time because the major source of such material vascular land plants had not yet evolved this along with a possibly lower degree of bioturbation contributed to enhanced pyrite formation and preservation and thus lower early paleozoic cs ratios

why plate tectonics was not invented in the alps in the alps folds were recognized in the early eighteenth century thrusts in the middle of the nineteenth century the nappe theory developed from 1884 to 1902 led to a mobilistic approach implying large scale relative movements of europe and of a prong of africa argand staub the existence of mesozoic oceans or ocean like basins was also realized ampferer introduced the concept of subduction verschluckung around 1935 alpine geologists somehow became afraid of their own courage and failed to present a coherent interpretation of the structure and evolution of the chain the theory of plate tectonics was developed primarily by geophysicists at sea who took little account of the alpine evidence

reactions of hydrothermal solutions with organic matter in paleoproterozoic black shales at talvivaara finland evidence from multiple sulfur isotopes abstract stable isotopic studies of archean paleoproterozoic sedimentary rocks older than 2 4 ga have documented large mass anomalous fractionations of sulfur isotopes 33 s 0 0 2 while younger rocks record little to no anomalous fractionation of sulfur isotopes this change from large anomalous fractionations to sulfur isotope values that fall on the terrestrial fractionation line has been proposed to represent the transition from an essentially anoxic archean atmosphere to an oxygenated atmosphere here we present 34 s and 33 s data for 28 core samples from paleoproterozoic 2 1 1 9 ga metamorphosed black shales and associated sulfide ores in eastern finland previous 34 s of studies of the talvivaara and outokumpu deposits of eastern finland focused on single grain analyses of sulfides while this study presents data from sequentially extracted sulfur fractions e g acid soluble sulfides chrome reducible sulfides elemental sulfur the sulfur isotope results range between 16 6 and 11 6 for 34 s 8 6 and 6 0 for 33 s and 1 25 and 0 55 for 33 s the anomalously fractionated samples are not consistent with previous findings that large anomalous fractionations of sulfur isotopes are absent in sedimentary metasedimentary rocks younger than 2 4 ga it is unlikely that talvivaara sulfides are the products of ultraviolet photolysis of volcanic so 2 in an oxygen poor atmosphere alternatively these sulfides could in part be the products of diagenetic reactions between sediments enriched in organic matter c org and hydrothermal solutions rich in sulfate i e thermochemical sulfate reduction laboratory experiments on thermochemical sulfate reduction have shown that mass anomalous fractionations of sulfur isotopes can be recorded in reduced sulfur products from reactions between simple amino acids and sulfate at 150 300 c a thermochemical sulfate reduction pathway for the mass anomalous signatures in talvivaara samples is consistent with previous genetic models proposed for the origin of the sulfur and organic carbon rich black shales now schists associated with the talvivaara and outokumpu ore deposits at talvivaara metalliferous black shales apparently were deposited under an anoxic to sulfidic marine water column the reported multiple sulfur isotopic data are key geological evidence for mass anomalous fractionations of sulfur isotopes during hydrothermal alteration of fine grained organic rich sediments approximately 20 of samples in this study show large offsets in 33 s values between different extracted sulfur fractions from the same sample which can be explained by classical isotope effects associated with the formation of hydrothermal alteration products that predominantly are retained within the precursor fine grained organic rich units

a metamorphosed proterozoic carbonaceous shale hosted co ni cu deposit at kalumbila kabompo dome the copperbelt ore shale in northwestern zambia the kalumbila co ni cu prospect 12 15 s 25 20 e is located 300 km west of the zambian copperbelt on the southeastern flank of the kabompo dome in the middle unit of the lufilian arc kalumbila contains a drill indicated resource of 3 04 mt at 0 67 wt percent ni 0 2 wt percent co and 0 11 wt percent cu using a 0 08 wt percent co and 0 3 wt percent ni cutoff with an average thickness of 12 75 m ni co cu mineralization occurs as strata bound disseminated to finely laminated locally semimassive to locally discordant chalcopyrite pyrrhotite violarite and siegenite within a finely laminated highly carbonaceous and pyritic metapelite 300 500 m thick surface rock exposure in this low relief terrain of woodland and seasonal swamp is 1 percent and geophysics magnetic and electromagnetic surveys is an essential exploration tool detrital zircons in the kalumbila metasediments shrimp u pb ages of 2004 1884 ma are derived from the underlying paleoproterozoic granitic gneiss such as that exposed in the adjacent kabompo basement dome the metasedimentary sequence grades upward from siliciclastic rocks mica schists to the carbonaceous metapelite which hosts the co ni cu these units are overlain by dolomitic and mg rich schists possible meta evaporites which are in turn succeeded by calc silicate rocks and a deformed diamictite this sequence is broadly similar to the stratigraphy in the zambian copperbelt and suggests that the kalumbila carbonaceous metapelite may be the chronostratigraphic equivalent of the katangan roan ore shale a significant exploration target kalumbila occurs within a moderately 40 north northwest dipping band of wamikumbi formation carbonaceous metapelite on the flank of a recumbent south southeast verging f1 or f2 back fold during the lufilian orogeny peak metamorphic conditions at f1 were of amphibolite facies grade 650 c 13 kbars both monazites and rutiles within the kalumbila metasediments have metamorphic characteristics and late orogenic lufilian shrimp u pb ages 548 6 7 6 ma and 531 21 ma respectively sulfides in the metasediments display metamorphic textures and therefore predate the peak of lufilian tectonism and thermal metamorphism a suite of spatially associated apparently late lufilian gabbros intrude the metasedimentary rocks these gabbros are unmineralized but the thermal effects of their emplacement may have modified ore distribution a genetic model in which synsedimentary pyrite in a carbonaceous pelite was partially replaced by syndiagenetic or metamorphic co ni cu bearing fluids of unknown origin is favored

euxinic conditions recorded in the ca 1 93 ga bravo lake formation nunavut canada implications for oceanic redox evolution abstract the composition of seawater changed dramatically during the initial rise of atmospheric oxygen in the earliest paleoproterozoic but the emerging view is that atmosphere ocean system did not experience an irreversible transition to a well oxygenated state instead it has been suggested that the oxygen content of the atmosphere ocean system decreased considerably after ca 2 06 billion years ago ga which resulted in a crash in marine sulfate concentrations the end of the deposition of major granular iron formations at ca 1 85 ga has been linked either to the development of extensive euxinic conditions along continental shelves or a decrease in hydrothermal flux the record of oceanic redox state is not well constrained for the period between ca 2 06 ga the end of the lomagundi positive carbon isotope excursion and ca 1 88 ga when major granular iron formations appeared we address this gap by presenting new iron speciation major and trace element data as well as sulfur organic carbon and molybdenum isotopic data for greenschist facies organic matter rich mudrocks orms of the ca 1 93 ga bravo lake formation piling group baffin island the iron speciation data suggest deposition of the bravo lake formation under a euxinic anoxic and sulfidic water column trace metal enrichments and mo isotope data suggest extensive marine euxinia ca 90 million years before the disappearance of large scale economic granular iron formations the addition of new mo data in this time interval is important as it contributes to filling in the sparse proterozoic record lastly this work provides further support for the idea that there was widespread anoxia shortly after the end of the lomagundi event

fifty years of the wilson cycle concept in plate tectonics an overview it is now more than 50 years since tuzo wilson published his paper asking did the atlantic close and then re open this led to the wilson cycle concept in which the repeated opening and closing of ocean basins along old orogenic belts is a key process in the assembly and breakup of supercontinents this implied that the processes of rifting and mountain building somehow pre conditioned and weakened the lithosphere in these regions making them susceptible to strain localization during future deformation episodes here we provide a retrospective look at the development of the concept how it has evolved over the past five decades current thinking and future focus areas the wilson cycle has proved enormously important to the theory and practice of geology and underlies much of what we know about the geological evolution of the earth and its lithosphere the concept will no doubt continue to be developed as we gain more understanding of the physical processes that control mantle convection and plate tectonics and as more data become available from currently less accessible regions

a missing link in the peri gondwanan terrane collage the precambrian basement of the moroccan meseta and its lower paleozoic cover this article provides stratigraphic and geochronological data from a central part of gondwana s northern margin the moroccan meseta domain this region located to the north of the anti atlas area with extensive outcrops of precambrian and lower paleozoic rocks has hitherto not received much attention with regard to its precambrian geology detrital and volcanic zircon ages have been used to constrain sedimentary depositional ages and crustal affinities of sedimentary source rocks in stratigraphic key sections based on this a four step paleotectonic evolution of the meseta domain from the ediacaran until the early ordovician is proposed this evolution documents the transition from a terrestrial volcanic setting during the ediacaran to a short lived carbonate platform setting during the early cambrian the latter then evolved into a rifted margin with deposition of thick siliciclastic successions in graben structures during the middle to late cambrian the detritus in these basins was of local origin

rare earth element geochemistry of standard sediments a study using inductively coupled plasma spectrometry the rare earth elements ree and y have been determined in 15 international standard sediments from france german democratic republic canada and the u s a samples were prepared using conventional rock dissolution techniques and the ree and y were separated from other constituents using cation exchange chromatography the ree la ce pr nd sm eu gd dy ho er yb lu and y were analysed simultaneously by inductively coupled plasma atomic emission spectrometry results indicate that u s g s standard shale sco 1 cody shale is a good reference material to use for the normalisation of the ree distributions of sediments data normalised to sco 1 are more readily interpreted than those normalised to existing estimates of average shale the ree patterns of standard sediments vary considerably in shape span an order of magnitude in absolute concentration and provide valuable reference values for the ree analysis of other sedimentary materials

history and geochemistry of a metalliferous sediment core from the mid atlantic ridge at 26 n fourteen thousand years of hydrothermal deposition are recorded in a metalliferous sediment core recovered from the trans atlantic geotraverse tag hydrothermal field on the mid atlantic ridge at 26 n an estimated 26 to 96 of the sediment at this core site is hydrothermally derived as determined from the caco3 al and fe data layers of essentially pure vent precipitates contain 3 caco3 and 0 5 al with high concentrations of fe 43 cu 4 1 zn 1 2 mn 1 1 v 480 ppm pb 175 ppm cd 32 ppm and hg 3 8 ppm sediment accumulation rates vary from 1 to 30 g cm2 1000 y throughout the core a function of the intensity of hydrothermal inputs distinct hydrothermal events are recorded at 6000 and 8500 y b p in layers containing 90 vent derived material vertical metal profiles and interelement relationships in the core result from variable deposition of oxides and sulfides oxidation and dissolution of sulfide phases and scavenging of metals from seawater

multiple sulfur isotopes of sulfides from sediments in the aftermath of paleoproterozoic glaciations geochemical evidence reported from paleoproterozoic sediments has long been used to evaluate the transition from the anoxic archean atmosphere to an oxygenated atmosphere sulfur isotopes 32s 33s 34s and 36s in sedimentary sulfides and sulfates are an especially sensitive means to monitor this transition such that the timing of the paleoproterozoic great oxidation event can be investigated using mass independently fractionated mif sulfur isotope systematics expressed as 33s here we report data from 83 individual analyses of pyrite pyrrhotite and chalcopyrite on a new suite of 30 different samples from finland south africa wyoming and ontario that span 600 my and follow one or several snowball earth events in the paleoproterozoic the samples were measured using a high resolution secondary ion mass spectrometry technique in multicollection mode that investigates multiple sulfur isotopes in microdomains 30 m within individual sulfide grains while preserving petrographic context we focused on sediments deposited in the aftermath of the paleoproterozoic glaciations between 1 9 and 2 2 ga to trace fluctuations in atmospheric o2 concentrations that were likely affected by an interplay of o2 sinks in the atmosphere and the upper ocean and continental crust and by the emergence and diversification of aerobic organisms our results demonstrate that mif sulfur isotopes are absent in sediments deposited after the period of protracted global cooling in the paleoproterozoic and independently confirm observations that mif ceased during this time we interpret our results by integrating 33s and 34s data in sulfides 13c data in carbonates and the estimated timing of glaciation events in the paleoproterozoic data strongly hint at the presence of microbial sulfate reduction and fluctuations in the concentration of dissolved seawater sulfate and or in 34ssulfate in the aftermath of glaciations and likely were affected by changing erosion rates and nutrient delivery to the oceans these changes modulated the population of primary producers especially oxygenic photosynthesizers and led to fluctuations in the abundance of atmospheric o2 co2 and ch4 our results support the interpretation that the world wide 13ccarb excursion observed between 2 25 and 2 05 ga karhu and holland 1996 was a period of significant accumulation of o2 in the atmosphere

tuzo wilson and the acceptance of pre mesozoic continental drift tuzo wilson s well known pre 1961 opposition to continental drift stemmed from his early experience as a geologist in the appalachians and the canadian shield which convinced him that orogenesis did not change drastically over geologic time conversely taylor in 1910 and wegener in 1912 hypothesized that continental drift began in cenozoic or mesozoic time between 1949 and 1960 tuzo wilson with adrian scheidegger developed a quasi uniformitarian model of progressive continental accretion around fixed archean nuclei tuzo abruptly jettisoned this model in 1961 when under pressure from paleomagnetic evidence for continental drift and a nascent concept of sea floor spreading he finally entertained the possibility of pre mesozoic as well as younger continental drift he immediately found it a superior fit to appalachian and shield geology while his uniformitarian conviction remained intact tuzo had blinded himself to the evidence for continental drift so long as he confined it to taylor or wegener s conception in continental drift operating continuously over geologic time he found a theory he could eagerly accept

northwest africa s ediacaran to early cambrian fossil record its oldest metazoans and age constraints for the basal taroudant group morocco abstract the anti atlas area in southern morocco preserves one of the most complete latest ediacaran to cambrian shallow marine carbonate records in the world and serves as a standard for global chemostratigraphic 13ccarb curves contrary to the excellent chemostratigraphic coverage neither metazoan fossils only stromatolites and calcified algae nor radiometric age constraints were hitherto available for the basal part of this carbonate record the tifnout member of the adoudou formation of the taroudant group we report an ediacara type fauna from shallow marine sandstones from the basal tabia member and microfossils from dolostones from both the tabia and the tifnout members of the adoudou formation the former are discoidal fossils and share many characteristics with the form genus aspidella and exhibit a peculiar style of preservation pointing towards an early diagenetic two stage carbonate followed by silica cementation history leading to good preservation of these supposedly once soft bodied organisms the dolostone hosted microfossils are preserved as sparite filled molds enclosed by a thin opaque envelope despite their small size they resemble late ediacaran calcifying metazoans such as namacalathus and tubular small shelly fossils together these fossils constitute the oldest known direct evidence for presumably metazoan life from northwest africa we also report new time constraints for the adoudou formation and fossils enclosed therein based on combined la icp ms and high precision ca id tims u pb zircon geochronology of detrital and volcanic zircons together with new chemostratigraphic 13ccarb and literature data these new age constraints suggest a late ediacaran age time span between ca 561 and 542 ma for the discoidal ediacara type fossils from the basal tabia member and a latest ediacaran to earliest cambrian time span between ca 544 and 540 ma and an early cambrian age time span between ca 528 and 523 ma for the two microfossil faunas from the tifnout member

chemical and mineralogical analysis of devonian black shale samples from martin county kentucky carroll and washington counties ohio wise county virginia and overton county tennessee u s a abstract core samples of devonian shales from five localities in the appalachian basin have been analyzed chemically and mineralogically the amounts of major elements are similar however the minor constituents organic c s phosphate and carbonate show ten fold variations in amounts trace elements mo ni cu v co u zn hg as and mn show variations in amounts that can be related to the minor constituents all samples contain major amounts of quartz illite two types of mixed layer clays and chlorite in differing quantities pyrite calcite feldspar and kaolinite are also present in many samples in minor amounts dolomite apatite gypsum barite biotite and marcasite are present in a few samples in trace amounts trace elements listed above are strongly controlled by organic c with the exception of mn which is associated with carbonate minerals amounts of organic c generally range from 3 to 6 and s is in the range of 2 5 amounts of trace elements show the following general ranges in ppm parts per million co 20 40 cu 40 70 u 10 40 as 20 40 v 150 300 ni 80 150 high values are as much as twice these values the organic c was probably the concentrating agent and the organic c and sulfide s together created an environment that immobilized and preserved these trace elements closely spaced samples showing an abrupt transition in color also show changes in organic c s and trace element contents several associations exist between mineral and chemical content pyrite and marcasite are the only minerals found to contain sulfide s in general the illite chlorite mixed layer clay mineral shows covariation with organic c if calcite is not present the enriched trace elements are not related to the clay types although the clay and organic matter are intimately associated as the bulk fabric of the rock

crustal conductors along the sveka profile in the fennoscandian baltic shield finland summary electrical properties of the crust in the central fennoscandian baltic shield are examined along the 435 km magnetotelluric profile sveka a 2 d geoelectric model shows large variations in the crustal resistivity with the model resistivities ranging from 0 1 to 35 000 m the main geoelectrical features of the crust and upper mantle are 1 a resistive archaean lower crust conductance 30 s 2 a conductive palaeoproterozoic lower crust beneath the central finland granitoid complex 170 900s free h2o rich fluids trapped into the lower crust seem less plausible causes for enhanced conductivity as long retention times are required and no possible sources seem to be available to produce fluids into the dry lower crust most likely causes for permanent enhancement of lower crustal conductivity include the conductive fill of ductile shear zones conductive graphite bearing lamellae conduction in mafic rocks perhaps via conduction in magnetite or conductive solid remnants of an ancient shear zone between two crustal blocks thin graphitic grain boundary films precipitated from co2 rich fluids also seem less plausible 3 a very resistive 10 000 35 000 m upper crust of the palaeoproterozoic central finland granitoid complex and the archaean domain 4 narrow and elongated conductors 0 1 100 m beneath the palaeoproterozoic kainuu ksb and tampere tsb schist belts are caused by graphite bearing metasedimentary rocks buried deep into the crust in the collisions of crustal terranes during the formation of the palaeoproterozoic svecofennian crust the 500 km long tsb conductor represents an internal svecofennian terrane boundary whereas the ksb conductor is a part of a discontinuous archaean proterozoic boundary conductor 5 resistive upper mantle there are no indications of an upper mantle conducting layer within the uppermost 300 km in the central part of the fennoscandian shield

the moroccan anti atlas the west african craton passive margin with limited pan african activity implications for the northern limit of the craton abstract the moroccan anti atlas region located south of the south atlas fault has been viewed traditionally as containing two segments separated by the anti atlas major fault these two segments are said to consist of a 600 700 ma pan african segment located in the northeast and b 2 ga eburnian segment situated to the southwest on the basis of observations in the zenaga and saghro inliers and of a recent literature review we suggest that this subdivision is inappropriate in that eburnian and pan african materials occur throughout the anti atlas region the entire anti atlas is underlain by eburnian crust unconformably overlain by a lower neoproterozoic passive margin allochthonous pan african ocean crustal slices were thrust onto the west african craton wac passive margin sequence 685 ma ago as a result of pan african accretion tectonics high level high k calc alkaline and alkaline granitoids locally intruded the anti atlas sequence as a whole at the end of the pan african orogeny at 585 560 ma the intervening 100 m y interval was marked by quiescence this succession of events can be related to the behaviour of one single rigid cratonic passive margin during an orogeny and correlated to the pan african events that occurred to the east in the tuareg shield and to the north in avalonian terranes this model implies that the actual northern limit of the wac is located at the south atlas fault saf and not at the anti atlas major fault aamf we propose that the aamf corresponds to the southwestern boundary of an aulacogen that formed along the northern margin of the wac during early neoproterozoic times this is consistent with the development of the gourma aulacogen on the eastern side of the wac this model further suggests that the northeastern boundary of the wac occurs north and not south of ougarta algeria support for this model is provided by geological and geophysical evidence

cave air control on dripwater geochemistry obir caves austria implications for speleothem deposition in dynamically ventilated caves there are very few process studies that demonstrate the annual variation in cave environments depositing speleothems accordingly we initiated a monitoring program at the obir caves an austrian dripstone cave system characterized by a seasonally changing air flow that results in a predictable pattern of high pco2 during summer and low pco2 in winter although similar seasonal changes in soil pco2 occur they are not directly connected with the changes in the subsurface since the dripwaters are fed from a well mixed source showing little seasonal variation cold season flushing by relatively co2 poor air enhances degassing of co2 in the cave and leads to a high degree of supersaturation of dripwater with regard to calcite forced calcite deposition during the cold season also gives rise to a pronounced pattern of synchronous seasonal variations in electrical conductivity alkalinity ph ca and 13cdic which parallel variations recorded in 13ccave air chemical components unaffected by calcite precipitation e g d 18o sio2 so4 lack a seasonal signal attesting to a long residence in the karst aquifer modeling shows that degassing of co2 from seepage waters results in kinetically enhanced c isotopic fractionation which contrasts with the equilibrium degassing shown from the soreq cave in israel the obir caves may serve as a case example of a dripstone cave whose seepage waters and speleothems show intra annual geochemical variability that is primarily due to chemical modification of the groundwater by a dynamic bidirectional subsurface air circulation

groundwater chemistry and cation budgets of tropical karst outcrops peninsular malaysia i calcium and magnesium abstract the discharge and chemical properties of 217 autogenic groundwaters were monitored over a 1 yr period in the tower karsts of central selangor and the kinta valley and in the setul boundary range because of differences in soil pco2 calcium concentrations are significantly higher in the boundary range mean 82 5 mg l 1 than in the tower karst terrain 44 6 mg l 1 local differences in both source area pco2 and amounts of secondary deposition underground cause marked intersite variability particularly in the tower karst dilution occurs during flood peaks in certain conduit and cave stream waters generally however calcium correlates positively with discharge since the amount of secondary deposition per unit volume of water decreases at higher flows magnesium concentrations and mg ca mg ratios of groundwaters are strongly influenced by bedrock composition though bedrock heterogeneity and the kinetics and equilibria of carbonate dissolution reactions preclude extremely low or high mg ca mg values net chemical denudation rates range from 56 6 to 70 9 m3km2yr 1 the results are considered in relation to cation fluxes in surface runoff soil throughflow and nutrient cycling preliminary calcium and magnesium budgets show that 1 dissolutional activity is largely confined to the near surface zone and 2 the annual uptake of calcium and magnesium by tropical limestone forests is similar in magnitude to the net solute output in groundwaters

dead carbon in stalagmites carbonate bedrock paleodissolution vs ageing of soil organic matter implications for 13c variations in speleothems twenty one 14c accelerator mass spectrometric analyses were obtained for three holocene stalagmites from the uamh an tartair cave sutherland scotland in order to estimate the past dead carbon proportion dcp results show that the dcp increases from 22 to 38 from 3780 years ago to the present because 13c variation is small within each sample it is concluded that this dcp increase is the product of the ageing of soil organic matter related to peat bog development above the cave that produced older soil co2 and not from a more intense dissolution of the surrounding carbonates which would have led to a 13c increase comparison with samples from other sites in europe shows no intersite correlation between dcp and 13c but a relatively good intersite correlation is observed between dcp and average site temperature thus temperature may be a major factor controlling the production of old soil organic matter co2 and therefore the dead carbon content of seepage water in contrast to the scotland stalagmites two other holocene samples from sites in southern france and belgium exhibit a good correlation between 13c and dcp which can be explained in terms of variations in the intensity of limestone dissolution consequently 13c variations observed in stalagmites are not always due to changes in the vegetation type c3 c4 as has been commonly assumed 13c 12c variations in speleothem calcite may also be controlled by the soil organic matter age and in some cases by the intensity of the limestone dissolution conversely a largely constant speleothem 13c signal as observed for the scotland stalagmites does not necessarily imply that surface climate and vegetation conditions were stable since the dcp variations in this case are clearly related to the peat bog development during stalagmite growth

stromatolitic bioherms and microphytolites from the late proterozoic draken conglomerate formation spitsbergen abstract the late proterozoic draken conglomerate formation akademikerbreen group in eastern spitsbergen displays several prominent stromatolitic bioherms in its lowermost beds the dolomitic bioherms are comprised principally of columnar stromatolites cf gymnosolenoides but include cross bedded microphytolitic grainstones the excellent exposures of the bioherms and microphytolitic grainstones along the margin of petrovbreen glacier and the exquisite preservation of structural and microscopic details permit the documentation and interpretation of these sedimentary and biological associations locally favorable ecologic circumstance or chance colonization initiated stromatolitic mat development which then became self perpetuating to form bioherms until rapid siliciclastic influx overwhelmed the mat building populations intermediate energy conditions in concert with microbial activity and inorganic processes generated the microphytolitic grainstones the interpretation of the biological and sedimentological interactions within these biohermal carbonates microphytolitic grainstones and siliciclastic rocks affords new insights into proterozoic paleoenvironments

temporal cycles of karst denudation in northwest georgia u s a time patterns of karst denudation in northwest georgia u s a were investigated at three spring sites for 12 months and at five stream sites for 10 years rainfall was evenly distributed and showed no significant seasonality at the springs as well as the streams water hardness was largely controlled by discharge at the springs soil pco2 and water ph were strongly correlated r 0 69 to 0 83 solute transport in spring waters was highly seasonal with two conduit flow springs removing more limestone in the winter and the diffuse flow spring removing more during the growing season at the stream sites most denudation occurred during the winter and spring seasons and least during the summer fourier analysis showed that variations in denudation occur on deterministic long wave as well as stochastic shortwave time scales as contributing variables discharge varied in short wave and long wave cycles whereas soil pco2 showed only a long wave cycle the 12 month deterministic cycles were the most important with changes in discharge taking precedence over soil pco2 time series regression explains up to 69 per cent of changes in denudation through rain and soil pco2 time cycles in available water are the key controlling factor of denudation and amounts of available soil co2 may not be as important in the temporal patterns of karst downwearing as has been believed previously

electromagnetic studies in the fennoscandian shield electrical conductivity of precambrian crust abstract electromagnetic em investigations of the 1980s in the fennoscandian baltic shield produced an unique and unified em data set studies include regional investigations by the magnetovariational mv method with large lateral sampling distance investigations of anomalous conductivity structures by magnetotelluric mt soundings and other em and electrical methods audio mt soundings d c dipole dipole and vlf resistivity profilings with shorter sampling distance and studies of the near surface conductivity by airborne em surveys the variety of methods provide an ability to map efficiently crustal conductivity structures from a regional scale of hundreds of kilometres down to local details of some metres in the anomalous structures the precambrian of the fennoscandian shield is characterized by roughly nw se directed elongated belts of conductors which separate more resistive crustal blocks the latter serve as transparent windows through which to probe deep electrical structure and belts of conductors as tectonic markers of ancient orogenic zones including 1 the kittila vetrenny poyas conductor 2 the lapland granulite belt and inari pechenga imandra varzuga conductors 3 the archaean proterozoic boundary conductor and 4 the southern finland conductor the conductive belts orogenic conductors indicate places where crustal masses collided and were finally sealed together enhanced conductivity in the orogenic conductors is caused primarily by an electronic conducting mechanism in graphite and sulphide bearing metasedimentary rocks estimations of the lower crustal conductivity indicate a laterally heterogeneous lower crust in the fennoscandian shield archaean lower crust seems to be in general more resistive than the early proterozoic lower crust of the karelian and svecofennian domains the lower crust in the southwestern part of the svecofennian domain and in the sveconorwegian domain seems to be more resistive than in the central part of the svecofennian domain

ni cu pge deposits in finland geology and exploration potential abstract several types of nickel sulphide deposits occur in finland some of them are also important sources of cu co and pge the main deposit types are related to archaean and palaeoproterozoic mafic to ultramafic rocks palaeoproterozoic metamorphosed black shales of the talvivaara type or the ultramafic and metasomatic calc silicate rocks of the ophiolitic outokumpu association several komatiite hosted ni cu pge deposits have been discovered in the archaean and paleoproterozoic greenstone belts in northern and eastern finland but only one has been briefly mined in 1989 many 2 44 ga palaeoproterozoic mafic ultramafic layered intrusions in finland host contact type pge ni cu deposits and significant reef type pge deposits typically the ni resources are of low grade but large tonnage the mafic ultramafic magmatism at ca 2 06 ga produced significant ni cu pge resources in the central lapland greenstone belt including the kevitsa and sakatti deposits the svecofennian domain in central and southern finland contains hundreds of small ca 1 88 ga mafic ultramafic orogenic intrusions many of these host nickel mineralization nickel exploration potential was evaluated in general based on identification of critical factors within a mineral system framework and a quantitative assessment of the potential occurrence of undiscovered nickel resources the mgo content of the parental magma was estimated for 28 deposits 6 komatiite hosted occurrences and 22 svecofennian orogenic intrusions the estimated mgo content of the parental magmas for the selected deposits varies from around 7 to 15 in basaltic to komatiitic basalt systems and up to 30 in more magnesian komatiitic systems the ni cu value varies mostly between 0 7 and 12 correlating in general positively with the mgo content of the magma exceptionally high or low ni cu values in some deposits may result from for example copper loss during post magmatic processes serpentinization and or metamorphism or part of the sulphide ore zoned by the ni cu value still being unknown recent advances in understanding of komatiites in finland indicates high exploration potential for nickel within the paleoproterozoic komatiitic formations which typically are also significantly enriched in cu and pge however the quantitative assessment of undiscovered nickel resources in finland suggests that the contact type ni cu pge deposits hosted by 2 44 ga mafic ultramafic layered intrusions in northern finland have the greatest potential for hosting undiscovered resources among the assessed nickel deposit types these occur within restricted areas resulting in a high deposit density finally considerable nickel resources might exist in undiscovered talvivaara kevitsa or sakatti type deposits these deposit types should be assessed as soon as more geological information becomes available