fluid inclusion studies of regionally extensive epigenetic dolomites bonneterre dolomite cambrian southeast missouri evidence of multiple fluids during dolomitization and lead zinc mineralization sources of basinal fluids that precipitated the dolomite hosted mississippi valley type orebodies of southeast missouri historically have been a subject of debate this study presents microthermometric data for fluid inclusions in the regionally extensive epigenetic dolomite at the base of the ore hosting bonneterre dolomite and in gangue dolomite of the viburnum trend pb zn district samples of epigenetic dolomite cover an area of more than 25 000 km 2 west of the st francois mountains and permit determination of regional variations of temperature and composition of the mineralizing fluids and possible fluid interactions homogenization temperature ice melting relationships temperature salinity among these inclusions document at least two end member fluid components a warmer less saline fluid 120 to 187 c 5 wt equiv nacl and a cooler more saline fluid 60 to 80 c 30 wt equiv nacl intermediate temperatures and fluid compositions indicate that the end member fluids likely mixed as they flowed through the region mixing was not confined to a stationary front but occurred throughout the study area comparison of homogenization temperatures to distance from possible basinal fluid sources indicates no discernible temperature gradient over the 25 000 km 2 study area the data are interpreted to indicate multiple basinal fluid interactions coeval with dolomitization and associated pb zn ore formation

relict non glacial surfaces in formerly glaciated landscapes abstract relict non glacial surfaces occur within many formerly glaciated landscapes and contain important information on past surface processes and long term landscape evolution relict non glacial surfaces are distinguishable from glacial surfaces by large scale morphologies including rounded summits fluvial valleys and cryoplanation terraces and pediments and the presence of tors blockfields and or saprolites preservation during glaciation occurs either through coverage by non erosive cold based ice or as nunataks although surface morphologies and denudation rates indicate a continuous non glacial surface history since preglacial times relict non glacial surfaces are dynamic features that have evolved during the quaternary depending on spatial variables such as lithology slope regolith depth and the abundance of fine matrix and water some surfaces are denuding very slowly while others display more rapid denudation high spatial variability in denudation rates results in changing surface morphologies over time denudation rates also display high temporal variability with much surface evolution having perhaps occurred soon after the initial onset of glaciation or during paraglacial phases while some parts of non glacial landscapes are currently active others may be largely inactive relicts of past higher energy regimes although non glacial surfaces are dynamic much remains to be determined regarding surface denudation rates and the magnitude of morphological changes over time

an asymptotic expansion for the recharge discharge model of enso abstractthe dynamics of el nino southern oscillation enso in the equatorial pacific ocean are largely associated with the slow thermocline adjustment at interannual and basin scales this adjustment involves among other things the fast propagation and reflection of equatorial waves by wind stress forcing a simple and straightforward asymptotic expansion of the long wave equations is proposed using the low frequency approximation the asymptotic expansion is performed in fourier space retaining only the gravest equatorial long waves and baroclinic modes with the largest scale and considering small dissipation by friction and boundary reflections this leads to an asymptotic model for the thermocline response to wind stress forcing which is in essence the ocean component of the recharge discharge model of enso the asymptotic model is nonheuristic and in broad agreement with some essential results scattered in previous studies thermocline variability is divided into a sloping tilt mode that adjus

sources of non glacial loess size quartz silt and the origins of desert loess abstract descriptions of peridesertic loess deposits and possible non glacial origins for silt size quartz are reviewed including direct release from weathered bedrock results from salt and frost weathering experiments are presented and methods by which sufficient energy can be imparted to sand size grains to release silt size fragments are identified these fragments may then be entrained by aeolian or fluvial action results from fluvial comminution experiments indicate that high energy mixed sediment fluvial systems may be very effective in generating quartz silt purely aeolian attrition is also seen as a major source of silt size and finer material results from aeolian abrasion experiments performed using crushed quartz sand are complemented by trials using sands from deeply weathered granite and pannonian sands from hungary field and laboratory observations are therefore seen to argue for the existence of deposits that can be classified as desert loess

electron microprobe and la icp ms study of monazite hydrothermal alteration implications for u th pb geochronology and nuclear ceramics this paper presents new data that quantify the response of magmatic monazite to three main types of hydrothermal alteration namely sericitization chloritization and greisenization the samples were taken from three paleozoic granites the st nectaire granite massif central france the carnmenellis granite cornwall england and the skiddaw granite lake district england fluid inclusion thermometry and hydrothermal parageneses indicate that alteration took place at temperatures ranging from 260 to 340 c and salinities from 3 to 18 wt nacl equivalent possible monazite alteration mechanisms found in the course of this study using backscattered scanning electron microscopy bse sem electron microprobe laser raman spectroscopy and laser ablation inductively coupled plasma mass spectrometry la icp ms include cationic substitutions monoclinic to hexagonal structure transition accompanied by chemical exchanges selective th removal dissolution reprecipitation and dissolution with replacement by a different mineral these results show that despite the compositional and crystallographic simplicity of monazite it exhibits varied chemical responses to different mineral fluid interactions elemental and isotopic measurements by la icp ms for the unaltered monazites yield statistically significant 232th 208pb and 238u 206pb magmatic crystallization ages in some cases it was possible to give a reasonable estimate of the age of mineral fluid interaction using the altered parts of the monazites or newly precipitated crystals for other minerals 232th 208pb and 238u 206pb systematics were strongly disturbed by variable inputs and or depletions of u th and pb the data suggest that monazite like nuclear waste forms would be good hosts for tetravalent actinides but may release the lanthanides and actinides with lower and higher valencies especially if the fluids are oxidizing or tend to dissolve monazite

regional trends in water chemistry smackover formation southwest arkansas geochemical and physical controls we present results on regional geochemical analyses of formation waters from jurassic carbonate strata of the upper smackover formation from the southwest arkansas shelf gulf coast basin these formation waters have been noted in earlier studies for their exceptional salinities and abnormally br rich composition our detailed and regionally extensive database shows that chemical heterogeneities occur on a relatively small scale and have spatial relations to faults which may act as pathways for fluid migration from deeper and hotter portions of the stratigraphic section one of the most pronounced heterogeneities in water chemistry is an h 2 s rich anomaly in the center of the shelf enrichments in h 2 s are accompanied by large increases in alkali elements li k and b and b which could be produced by higher temperature diagenesis of clay minerals and feldspars in deeper seated siliciclastic strata bromide enrichments in all smackover formation waters are apparent from relations between br and cl contents as well as br and divalent cation carpenter function values as suggested by earlier studies of these waters evaporatively concentrated seawater expelled from associated thick monomineralic evaporite sections may be an important source of br cl and na whereas ca mg and sr concentrations have been modified by carbonate mineral recrystallization and dolomitization mineral equilibria exert significant controls on concentrations of ca mg sr and so 4 in these brines br enrichment likely was produced by halite recrystallization in fluids already enriched in br from seawater evaporation elevated cl br ratios occur in regional association with lower salinity water near t e south arkansas fault system consistent with halite dissolution during meteoric water recharge thus despite relatively uniform reservoir lithology and simple structural setting processes on small spatial scales have resulted in significant heterogeneity in water chemistry within a small area of the gulf coast sedimentary basin although movement of fluids along these fault systems is not demonstrated in our study the regional trends in geochemistry are strongly suggestive of their important role in controlling chemical heterogeneities in smackover formation waters

origin and chemical evolution of formation waters from silurian devonian strata in the illinois basin usa abstract a suite of formation water samples from silurian devonian reservoirs in the illinois basin has been analyzed for major minor and trace element concentrations and for h o and sr isotopic compositions in order to interpret origin of salinity and geochemical evolution of brine compositions in this evaporite and shale poor cratonic basin although chloride concentrations range from 2000 to 137 000 mg l cl br ratios 291 18 are consistent with those of seawater or seawater evaporated short of halite saturation cl br 292 thus during silurian devonian time subaerially evaporated penesaline brine entered the subsurface where it was chemically modified through brine rock interactions cation br ratios and mineralogy of associated strata indicate that na and k were depleted through interaction with clay minerals ca was enriched and mg depleted by dolomitization and sr was enriched as a result of caco3 recrystallization and dolomitization although significant dilution of the modified brine with meteoric water is supported by d 18o covariance original marine waters have not been completely expelled from silurian devonian strata hydrogen and oxygen isotopes exhibit covariant relations with cation and anion concentrations implying that isotopic exchange between h2o and minerals has not greatly influenced the d 18o trend brine 87 sr 86 sr ratios range from 0 7092 to 0 7108 when these ratios are plotted versus 1 sr a two component mixing trend is suggested although sr concentrations have experienced local diagenetic modification a 87sr enriched fluid may have accompanied petroleum migration from new albany shales into adjacent silurian devonian carbonates where it mixed with remnant evaporated seawater this event probably preceded the influx of meteoric water as gdd and 18o are not correlated with sr isotopic compositions of formation waters

on the physical interpretation of the lead relation between warm water volume and the el nino southern oscillation the warm water volume wwv a proxy for the equatorial pacific heat content is the most widely used oceanic precursor of the el nino southern oscillation enso the standard interpretation of this lead relation in the context of the recharge oscillator theory is that anomalous easterlies during e g la nina favour a slow recharge of the equatorial band that will later favour a transition to el nino here we demonstrate that wwv only works as the best enso predictor during boreal spring i e during enso onset in both observations and cmip5 models at longer lead times the heat content in the western pacific wwvw is the best enso predictor as initially formulated in the recharge oscillator theory using idealised and realistic experiments with a linear continuously stratified ocean model and a comprehensive wave decomposition method we demonstrate that spring wwv mostly reflects the fast kelvin wave response to wind anomalies early in the year rather than the longer term influence of winds during the previous year wwv is hence not an adequate index of the slow recharge invoked in the recharge oscillator the wwvw evolution before spring is dominated by forced rossby waves with a smaller contribution from the western boundary reflection wwvw can be approximated from the integral of equatorial wind stress over the previous 10 months thus involving a longer term time scale than wwv main time scale 3 months we hence recommend using wwvw rather than wwv as an index for the slow recharge before the spring predictability barrier

basement unconformity control on alteration st francois mountains se missouri the basement lamotte formation unconformity in southeastern missouri shows evidence of several distinctive alteration events some of which may be related to migration of ore forming fluids or k rich basinal brines the alterations are spatially related to the unconformity suggesting that the unconformity was a preferred pathway for fluid migration unconformity related rocks in five cores penetrating both the lamotte formation and the basement have been characterized by bulk chemistry mineralogy textures and paleotopographic position the alteration history along the unconformity includes 1 pre lamotte hydrothermal alteration affecting basement 2 pre lamotte weathering and 3 post lamotte hydrothermal and diagenetic events the third group is particularly complex including early diagenetic hematite and calcite cementation later quartz cementation secondary biotite growth k metasomatism that generated adulaira and k leaching that left a narrow dickite rich zone along the unconformity sev

is enso a cycle or a series of events 1 after early ideas that saw el ninos as isolated events the advent of coupled models brought the conception of enso as a cycle in which each phase led to the next in a self sustained oscillation twenty two years of observations that represent the el nino and la nina peaks east pacific sst and the memory of the system zonal mean warm water volume suggest a distinct break in the cycle in which the coupled system is able to remain in a weak la nina state for up to two years so that memory of previous influences would be lost similarly while the amplitude of anomalies persists from the onset of a warm event through its termination there is no such persistence across the la nina break these observations suggest that el ninos are in fact event like disturbances to a stable basic state requiring an initiating impulse not contained in the dynamics of the cycle itself

lead and sulfur isotope microstratigraphy in galena crystals from mississippi valley type deposits the development of an analytical procedure for lead and sulfur isotope analysis by secondary ion microprobe mass spectrometry allowed us to provide in situ isotopic microanalyses of galena crystals we performed analyses across the growth zones of two crystals of galena from mississippi valley type ore deposits with a spatial resolution of 50 mu m and a spacing of 250 mu m these analyses show frequent variations for both lead and sulfur isotope compositions which occurred during the time of the crystal growth we can demonstrate that for both elements these variations involved changes in the sources of the brines which formed the ore deposits the comparison of lead and sulfur isotope behavior suggests that for the picher deposit lead and sulfur originated from common sources whereas for the buick mine deposit lead and sulfur had separate sources the two galenas exhibit rapid and frequent changes in isotopic composition this suggests numerous and discontinuous inputs of lead and sulfur to the ore deposits this model agrees well with a physical model for mississippi valley type deposits proposed by cathles and smith 1983 the isotopically different sources were probably different sedimentary layers and perhaps basement rocks in the same basin whose formation waters were channeled in preferred water conduits to the ore deposit location during the subsidence of the basin allowing mixing between the different sources to occur during the brines travel

strontium isotopic constraints on the origin of ore forming fluids of the viburnum trend southeast missouri abstract we have measured 87 sr 86 sr and rb and sr concentrations in several minerals primarily sulfides spanning the paragenesis of hydrothermal mineralization in the viburnum trend in southeast missouri separate measurements were made for fluid inclusions opened by crushing or thermal decrepitation and for the solids for comparison measurements were also made on samples of probable local aquifers the bonneterre formation and the lamotte sandstone for some of the samples concentrations of k ca cl na and mg are also reported in several cases 87 sr 86 sr ratios are different higher in the solids than in the fluid inclusions we have investigated the possibility that either type of sample gives spurious results e g that the fluid inclusions are secondary or contaminated by host dolomite or that sr in the solids reflects a detrital rather than an authigenic source consideration of mass balance overall solute chemistry and examination of non sulfide dissolution residue however suggests that both types of sample reflect primary fluid sr composition we thus adopt the working hypothesis that sr isotopic composition in fluids at the time of hydrothermal mineralization was highly variable the observed results for the viburnum trend do not conform well to expected trends for mississippi valley type mvt mineralization based primarily on analyses of gangue carbonates barite and fluorite fluid inclusion sr in some of the viburnum trend samples is more radiogenic than in the host dolomite but only moderately so in other samples notably main stage octahedral galena fluid inclusion sr composition is within the range observed for the host dolomite in contrast sr in some of the sulfides is very radiogenic much more so than previously reported for mvt minerals and is very radiogenic early in the paragenesis pyrite chalcopyrite sphalerite less radiogenic during main stage ore deposition and again more radiogenic in later paragenetic stages

constraints from fluid inclusions on sulfide precipitation mechanisms and ore fluid migration in the viburnum trend lead district missouri measurements on fluid inclusions in hydrothermal dolomite cements place constraints on sulfide precipitation mechanisms and on the thermal hydrologic processes which formed the viburnum trend mississippi valley type lead district homogenization temperatures and freezing point depressions were determined for fluid inclusions in bonneterre dolomite hosted dolomite cements in mine samples as well as drill core from up to 13 km outside of the district a well defined cathodoluminescent zonation distinguishes dolomite growth zones in the vi burnurn trend as older or younger than main stage mineralization octahedral galena and facilitates correlation with other dolomites outside the viburnum trend homogenization temperatures and salinities in samples from mines are not systematically different from those of samples outside of the district medians of homogenization temperature distributions differ by not more than 25 degrees c so that a temperature gradient if present should not have exceeded approximately 25 degrees c within the study area these observations are interpreted to indicate that the viburnum trend was not strongly thermally anomalous with respect to surrounding country rock and that fluid flow occurred on a broad scale through not only the lamotte sandstone but through the overlying cambrian carbonates as well the absence of a significant recognizable decrease in temperature either vertically within the section or east west across the district coupled with the minor amount of silica in the district argues against cooling as a primary cause of sulfide precipitation fluids whose primary aquifer was the lamotte sandstone predominantly a quartz arenite should have been in equilibrium with quartz quartz in the viburnum trend occurs as a minor drusy vug lining phase but the district lacks the intense silicification found in other mississippi valley type districts such as tri state oklahoma kansas missouri quartz solubility is strongly temperature dependent and under equilibrium conditions a decrease of 10 degrees c or more should have precipitated at least as many moles of silica as galena assuming a galena solubility of between 1 and 10 ppm clearly this is not the case as galena is far more abundant than quartz in the viburnum trend ice final melting temperatures t m in fluid inclusions generally range from 14 degrees to 27 degrees c for primary dolomite hosted inclusions using these t m values and cation ratios for the inclusion fluids absolute concentrations for the individual cations and chloride were calculated using the thermochemical model of spencer et al 1990 the corresponding high but variable salinities 3 9 to 5 9 chloride molality are evidence for the presence of more than one distinct fluid during mineralization in a reduced sulfur mineralization model with pb carried as chloride complexes dilution is also a possible sulfide precipitation mechanism the difference in pb solubility for an equal quantity of reduced sulfur in the extremes of the chloride concentration range 3 9 vs 5 9 molal reaches 1 ppm only for ph values below approximately 4 5 accepting 1 ppm as a minimum metal concentration for a viable ore forming fluid dilution only appears capable of precipitating sulfides in a fluid with ph near the lower limit of values considered geologically reasonable or attainable dolomite cements hosting warm approximately 105 degrees 125 degrees c saline fluid inclusions are ubiquitous in the porous dolomitic facies of the bonneterre dolomite based on stratigraphic reconstructions however it is unlikely that the bonneterre was buried deeper than 1 5 km the distribution of warm inclusions beyond the viburnum trend district implies that fluid migration was regional in scale fluid inclusion temperatures inconsistent with typical basement heat flow controlled geothermal gradients 25 degrees 35 degrees c km may be explained by long distance migration of warm basin derived brines elevated temperatures observed in fluid inclusions at shallow stratigraphic depths are consistent with a gravity flow hydrologic system characterized by rapid flow rates and the capacity for advective heat transport

the significance of rb sr glauconite ages bonneterre formation missouri late devonian early mississippian brine migration in the midcontinent rb sr mean model ages of 370 plus minus 10 ma for glauconites from the cambrian lower bonneterre formation in southern and central missouri are in excellent agreement with a rb sr isochron age of 359 plus minus 22 ma for glauconites from the magmont mine viburnum trend in the southeast missouri lead district the lower bonneterre and magmont mines ages probably reflect isotopic resetting most likely associated with dolomitization and or mississippi valley type ore formation in the southeast missouri lead district the temporal relation between widespread dolomitization and ore formation in missouri is unclear but mounting evidence for two devonian disturbances permits the following interpretation 1 a devonian timing 380 400 ma for widespread dolomitization and 2 a late devonian early mississippian timing 360 370 ma for ore formation in southeast missouri late devonian early mississippian fluids associated with the earliest stages of collisional tectonics and metamorphism to the south and southeast may have been important in the formation of southeast missouri ore deposits these tectonically driven waters may themselves have been the mississippi valley type ore fluids entering missouri by way of the black warrior basin and reelfoot rift and or the arkoma basin alternatively the movement of orogenic fluids hundreds of kilometers distant may have initiatedmore and distally influenced the migration of more locally derived mississippi valley type ore fluids broad regions of missouri and adjacent areas experienced heating and crustal flexing in the late devonian and consequently preservation of elevated temperatures in mississippi valley type fluids as they move great lateral distances may not be necessary for ore formation in southeast missouri less

introduction and background interpretations of landscape change research into the origins of landscape has a long and distinguished tradition in america landscape studies form the core of physical geology while elsewhere the study of landscape development has spread beyond the confines of geology to develop a firmer foothold in the geographical tradition particularly in geomorphology the development of ideas in landscape study has however been neither steady nor sequential it has been characterized instead by several major conceptual shifts interspersed with periods of reinforcement or neglect within geomorphology and certainly within the english speaking world the most important of these shifts occurred in the early 1960s with the move from denudation chronology of landscapes as a core activity to an emphasis on process based investigation of individual landforms in geology the 1960s also marked an important change in perspective publication of plate tectonic theories sea floor spreading continental drift subduction and mountain building had far reaching consequences for all earth science in particular plate tectonics made the study of apparently ancient processes billions of years old applicable to the present day with for example application to earthquake studies whilst the initial shift towards process studies was a response to the desire for a better understanding of the mechanisms driving landscape change it was not long before this goal became relegated in the eyes of many of its practitioners as a consequence process study became an end in itself rather than a means to an end this movement has been reinforced in recent years by a demand for greater relevance from for example research funding bodies resulting in an emphasis on problem solving and wealth generation that has moved away from studies at the landscape scale consequently within geomorphology process studies and applied geomorphology have come to dominate the literature a dominance reinforced by the increasing division and separation of the discipline into process domains such as fluvial and glacial studies this has reached the point where many researchers would now naturally identify themselves as specialists in a particular process rather than as geomorphologists a similar trend can be identified within geology whereby studies of uplift erosion and stability clearly fall into pre plate tectonics and post plate tectonics generations in the 1920s studies of denudation were popular as evidenced by the volume of work conducted in southern england and based largely on observations of palaeovaueys tilted strata and unconformities sediment provenance became important in the 1920s and 1930s and early works on the use of heavy minerals in studies of past erosion were developed by the 1960s geologists were standing back and viewing many processes in terms of their global plate tectonic significance however this emphasis on processes inevitably led to the development of more labour intensive analytical methods as a consequence of which the wider perspective began to be neglected through the 1970s and 1980s therefore studies of uplift developed using methods that determine heating or pressurization of the uplifted rocks thermal estimates of uplift including spore or conodont alteration indexes fluid inclusion studies and diagenetic models were developed together with estimates of pressurization including studies of mineralogy and sonic borehole logs however perhaps the most significant advance in the determination of uplift rates and amounts has been in the field of apatite fission track analysis afta carter 1999 the widespread use of afta in the oil industry has provided large datasets that encompass the offshore basins formerly ignored by those concerned with land erosion buchanan buchanan 1995 studies of erosion and palaeoerosion have also developed from the study of derived clasts to clay minerals and heavy minerals requiring increasingly labourintensive and hence specialist methods to derive local or even regional perspectives specialization clearly has many advantages if however it is allowed to proceed unchecked these advantages eventually come to be outweighed by the effects of an increasingly reductionist approach whereby concentration on small scale studies and the pursuit of ever greater detail detracts from appreciation of the largescale picture and ultimately fragmentation and loss of the subject core clearly the longer this reductionist segregationist approach persists the more difficult it is to define and to justify the existence of the original parent discipline

regional epigenetic dolomitization in the bonneterre dolomite cambrian southeastern missouri a dolomite bed averaging 6 m in thickness forms the base of a limestone and shale facies of the bonneterre dolomite cambrian southeastern missouri the dolomite immediately overlies the lamotte sandstone and covers an area of more than 16 600 km 2 it is proposed that this basal dolomite formed as a result of interaction with warm basin derived water circulating through the underlying lamotte sandstone and that the dolomitization event coincided with the emplacement of mississippi valley type sulfide ores in the nearby viburnum trend this hypothesis is supported by 1 petrographic evidence that suggests an origin at temperatures 50 c 2 cathodoluminescent microstratigraphy of dolomite cements which is correlative with that in gangue dolomite cements in the nearby orebodies and 3 stable oxygen and carbon isotope values that are consistent with a basinal origin of the dolomitizing water the basal dolomite bed may represent one of the most extensive epigenetic dolomites yet documented this implies that a basinal water can alter rocks over a wide area at a considerable distance from its source

paleomagnetic and petrographic investigation of the taum sauk limestone southeast missouri paleomagnetic results from 17 sites in one quarry of the cambrian dresbachian stage taum sauk limestone member bonneterre formation reveal two components of magnetization on the basis of thermal demagnetization coercivity spectrum analysis and petrographic evidence both components reside in hematite sites can be divided into three groups based on behavior during thermal demagnetization and petrographic criteria the first group consists of massive pink limestones and contains a component with declination 270 inclination 11 corresponding to a cambrian pole at 175 6 e 3 6 s the second group of sampling sites consists of specimens with numerous burrows filled with hematite intergrown with calcite the sites are dominated by the second component of magnetization which has declination 147 and inclination 10 and corresponds to a reversed pole position at 133 1 e 37 3 n a significant fraction of this component which is interpreted to be carboniferous in age resides in hematite intergrown with calcite in the burrows petrographic relationships indicate that the calcite and hematite were acquired before dolomite which places a maximum age on dolomitization the third group consists of massive pink limestones with variable amounts of burrowing and contains both directions of magnetization in roughly equal proportions with closely overlapping blocking temperature spectra the presence of two stable directions of magnetization from one location with neither being dominant or even present throughout the quarry indicates the significant effect that diagenetic and sedimentologic processes may have on the magnetization of sedimentary units

a younger dryas plateau icefield in the monadhliath scotland and implications for regional palaeoclimate a record of younger dryas glaciation in scotland is well established however the role of the monadhliath a significant plateau area extending over 840 km2 in central scotland has never been investigated systematically we present the first systematic glacial geomorphological mapping across the whole region which has led to the identification of hitherto unrecorded glacial and associated landforms the spatial distribution of these landforms indicates that the last phase of glaciation in the area was that of a local plateau icefield in addition a clear morphostratigraphical signature provides a strong indication that the icefield dates to the younger dryas 12 9 11 7 ka which is supported by numerical ages in the southeast of the study area based on the geomorphological evidence and 2d glacier surface profile modelling a 280 km2 icefield is reconstructed a novel approach is introduced to quantify plateau icefield thickness for equilibrium line altitude ela and palaeoprecipitation calculations resulting in greater overall data confidence compared to traditional reconstruction methods the ela for the whole icefield is calculated to be 714 25 m whilst the elas of individual outlet glaciers range from 560 m in the west to 816 m in the east demonstrating a significant w e precipitation gradient across the region during the younger dryas these elas compare well with those calculated for younger dryas ice masses reconstructed in neighbouring regions and are in good agreement with overall precipitation patterns suggested for scotland during this time whilst the total amount of precipitation calculated from these elas is highly dependent on the method used irrespective of this the study suggests a more arid younger dryas climate in the region compared to the present day

sorted clastic polygons in the argyre region mars and possible evidence of pre and post glacial periglaciation in the late amazonian epoch abstract the argyre basin and associated rim materials in the southern highlands of mars are ancient having been formed by the impact of a large body 3 9 gya despite its age the regional landscape exhibits a wide range of geological geomorphological modifications and or features e g fluvial lacustrine aeolian glacial and periglacial collectively this bears witness to the dynamic evolution of the argyre region from the deep past through to perhaps the present day here we present three principal findings that point to at least two distinct episodes of periglaciation separated by a possible glacial interval during the very late amazonian epoch in eastern aonia terra at i e on the western flank of the argyre basin these findings are the product of our circum argyre study of all hirise images 35 65 s and 290 350 e 1 a the first periglacial episode involves the development of small sized 15 25 m in diam and clastically sorted polygons sps the sps are observed at eighteen locations within eastern at hitherto the presence of sps in this region has been reported at one location alone no other observations of sps in the southern hemisphere of mars have been documented morphologically similar landforms develop in cold climate permafrost landscapes on earth by means of periglacial processes i e freeze thaw cycling segregated ice formation cryoturbation and frost heave b we ascribe a periglacial origin to the sps in eastern at on the basis of this similarity of form and no less importantly on the close spatial association of the sps with blockfields whose weathered clastic products are the building blocks of periglacial sorting on earth gelifluction like lobes and possible wet gullies where similar assemblages occur in terrestrial permafrost landscapes the presence of liquid water and of boundary conditions tolerant of freeze thaw cycling are observed or inferred c fifteen of the eighteen sp locations are clustered longitudinally 44 4 57 5 s 289 9 302 4 e this is inconsistent with the latitudinal and obliquity driven dependency of freeze thaw cycling in the late amazonian epoch hypothesised by many workers in the discipline 2 the second periglacial episode is highlighted by the development of small sized and clastically non sorted polygons nsps these polygons could have formed by means of a dry cryotic process i e thermal contraction cracking 3 the nsps incise and thus postdate a light toned mantle thought by numerous workers to comprise an ice dust admixture at some of the locations where the putatively icy mantle has undergone apparent ablation underlying sps are observed this suggests that the sps predate the mantle and derivatively the nsps as well the proposed geochronology of wet based sp icy mantle dry based nsp periods and interval is entirely new to the community moreover it underlines the possibility that periglacial and glacial boundary conditions at least in our study area may have oscillated much more substantially in the very late amazonian epoch than many workers have thought possible

observations of warm water volume changes in the equatorial pacific and their relationship to el nino and la nina abstract this paper describes observed changes in surface winds sea surface temperature sst and the volume of water warmer than 20 c wwv in the equatorial pacific ocean for the period 1980 99 the purpose is to test recent hypotheses about the relationship between variations in wwv and the el nino southern oscillation enso cycle the results confirm inferences based on theory models and previous empirical analyses using proxy data namely sea level that enso involves a recharge and discharge of wwv along the equator and that the cyclic nature of enso results from a disequilibrium between zonal winds and zonal mean thermocline depth the authors also find that the magnitude of enso sst anomalies is directly related to the magnitude of zonal mean wwv anomalies furthermore for a given change in equatorial wwv the corresponding warm el nino sst anomalies are larger than the corresponding cold la nina anomalies this asymmetry between the warm and cold phases of the enso cycle implies differences

metal rich fluid inclusions provide new insights into unconformity related u deposits athabasca basin and basement canada the paleoproterozoic athabasca basin canada hosts numerous giant unconformity related uranium deposits the scope of this study is to establish the pressure temperature and composition p t x conditions of the brines that circulated at the base of the athabasca basin and in its crystalline basement before during and after uo2 deposition these brines are commonly sampled as fluid inclusions in quartz and dolomite cementing veins and breccias associated with alteration and u mineralization microthermometry and laser ablation inductively coupled plasma mass spectrometry la icp ms data from five deposits rabbit lake p patch eagle point millennium and shea creek complement previously published data for the mcarthur river deposit in all of the deposits investigated fluid inclusion salinity is between 25 and 40 wt nacl equiv with compositions displaying a continuum between a nacl rich brine end member cl na ca mg k and a cacl2 rich brine end member cl ca mg na k the cacl2 rich brine has the highest salinity and shows evidence for halite saturation at the time of trapping the continuum of compositions between the nacl rich brine and the cacl2 rich brine end members combined with p t reconstructions suggest anisothermal mixing of the two brines nacl rich brine 180 30 c and 800 400 bars cacl2 rich brine 120 30 c and 600 300 bars that occurred under fluctuating pressure conditions hydrostatic to supra hydrostatic however because the two brines were u bearing and therefore oxidized brine mixing was probably not the driving force for uo2 deposition several scenarios are put forward to account for the cl na ca mg k composition of the brines involving combinations of seawater evaporation halite dissolution mixing with a halite dissolution brine mg ca exchange by dolomitization na ca exchange by albitization of plagioclase na k exchange by albitization of k feldspar and mg loss by mg rich alteration finally the metal concentrations in the nacl rich and cacl2 rich brines are among the highest recorded compared to present day sedimentary formation waters and fluid inclusions from basin hosted base metal deposits up to 600 ppm u 3000 ppm mn 4000 ppm zn 6000 ppm cu 8000 ppm pb and 10 000 ppm fe the cacl2 rich brine carries up to one order of magnitude more metal than the nacl rich brine though the exact origin of major cations and metals of the two brines remains uncertain their contrasting compositions indicate that the two brines had distinct flow paths and fluid rock interactions large scale circulation of the brines in the athabasca basin and basement was therefore a key parameter for metal mobility including u and formation of unconformity related u deposits

organic maturation and ore precipitation in southeast missouri the sulfate reduction plus mixing hypotheses for the formation of mississippi valley type deposits have suffered from an inability to show a plausible mass balance between sulfate possible reductants and sulfide ores and a mechanism for mixing the reduced gas h 2 s with the metal bearing fluid both these problems are resolved by focusing on the gases mostly methane generated from the organic matter in the host carbonate rocks during thermal maturation caused by heat from the hydrothermal solutions in southeast missouri it appears that the volume of the bonneterre formation required to produce all the methane needed to reduce enough sulfate to precipitate all the ores is approximately the same as the volume of the brown rock facies which hosts most of the ore therefore it appears that metal and sulfate bearing solutions entered the bonneterre at lamotte sandstone pinchouts then followed permeability trends which coincided mainly with the oolitic grainstones associated with the stromatolite reef most of which are brown evolution of methane and other reducing compounds from the brown rock resulted in sulfate reduction and precipitation of sulfides several other regional and local factors in the geology of the area are found to be compatible with this idea

remagnetization by basinal fluids testing the hypothesis in the viola limestone southern oklahoma migration of orogenic or basinal fluids is a recently invoked mechanism to explain the widespread presence of late paleozoic secondary magnetizations in the rocks of north america paleomagnetic and geochemical results from the ordovician viola limestone in southern oklahoma are evaluated to assess the role of basinal fluids in leading to secondary magnetizations in the unit the viola limestone contains what we interpret to be a pervasive pennsylvanian synfolding magnetization residing in magnetite and a localized permian magnetization which resides in hematite and occurs in alteration zones around mineralized veins both secondary magnetizations are interpreted as chemical remanent magnetizations crm based on low burial temperatures and the presence of authigenic magnetic phases the relative proportion of the permian crm in hematite gradually decreases whereas the magnetite crm increases with distance from the veins fluid inclusion and sr isotope studies indicate that the vein mineralization calcite with mississippi valley type oxides and sulfides precipitated from basinal fluids which were warm saline and radiogenic the radiogenic 87sr 86sr values of the limestones in the alteration zones and the fact that there is more significant alteration closer to the veins suggests that the basinal fluids were also responsible for alteration in the limestones the coincidence of the geochemical and remagnetization trends suggests that the permian crm dates the migration of basinal fluids through the veins geochemical results from the viola limestone containing the pervasive crm indicate that it is relatively unaltered with no evidence for basinal fluids the lack of evidence for basinal fluids suggests that other mechanisms for the origin of the pervasive crm need to be tested the results of this study indicate that flow of basinal fluids was focused in veins and only locally altered the host limestone

the geomorphological and geological importance of palaeosurfaces this special publication is a collection of papers which identifies describes and interprets the occurrence of palaeosurfaces in the geological record the concept of a palaeo surface is one which is generally understood across the geomorphological and geological sciences but according to discipline and application often differs in the emphasis and detail of its interpretation in order to encompass the widest range of contributions and views upon the subject of palaeosurfaces a broad remit was deliberately adopted during the preparation of this volume cations of ancient palaeosurfaces the research areas represented are geographically widespread and include examples from australia africa south america india and europe

rbsr and kar ages of paleozoic glauconites from ohio indiana and missouri u s a abstract glauconite pellets from the lower silurian brassfield formation on both limbs of the cincinnati arch in ohio and indiana give a rb sr age of 370 11 ma which is substantially younger than the stratigraphic age of the formation the age is concordantcwith conventional k ar ages of 355 6 and 368 5 ma for two of the same glauconites concordant ages were also obtained from the viburnum trend in missouri where glauconite pellets from the davis formation in an ore zone collapse structure into the underlying bonneterre formation give a rb sr age of 387 21 ma and conventional k ar ages of 368 5 and 369 5 and 369 5 ma a third suite of glauconite from the bonneterre formation in the old lead belt 10 km from the nearest ore body has given a rb sr age of 423 7 ma and slightly older conventional k ar ages of 434 6 445 6 and 441 11 ma because these glauconite bearing rocks have been buried to depths of less than 1 km thermal resetting of the rb sr and k ar systematics appears unlikely the initial 87 sr 86 sr ratios of the rb sr isochrons are similar to the ratios for vein and vug filling dolomite and calcite this is consistent with resetting of the rb sr and k ar systems during diagenetic changes which included the isotopic equilibration perhaps by cation exchange of the sr in the glauconite with that in the diagenetic and mississippi valley type ore fluids this interpretation implies that the age of the mississippi valley type mineralization in the viburnum trend is devonian rather than carboniferous permian as has been inferred from paleomagnetic measurements cation exchange experiments with a dilute sr bearing solution and an artificial oilfield brine indicate that glauconite adsorbs large amounts of sr some of which is sufficiently strongly attached to the glauconite lattice as to resist leaching with ammonium acetate the introduction of this strongly attached sr may be the first step in the resetting of the rb sr systematics of glauconite by cation exchange

geochemistry of metal rich brines from central mississippi salt dome basin u s a abstract oil field brines are the most favored ore forming solutions for the sediment hosted mississippi valley type ore deposits detailed inorganic and organic chemical and isotope analyses of water and gas samples from six oil fields in central mississippi one of the very few areas with high metal brines were conducted to study the inorganic and organic complexes responsible for the high concentrations of these metals the samples were obtained from production zones consisting of sandstone and limestone that range in depth from 1900 to 4000 m 70 120 c and in age from late cretaceous to late jurassic results show that the waters are dominantly bittern brines related to the louann salt the brines have extremely high salinities that range from 160 000 to 320 000 mg l total dissolved solids and are na ca cl type waters with very high concentrations of ca up to 48 000 mg l and other alkaline earth metals but with low concentrations of aliphatic acid anions the concentrations of metals in many water samples are very high reaching values of 70 mg l for pb 245 mg l for zn 465 mg l for fe and 210 mg l for mn the samples with high metal contents have extremely low concentrations 2 s samples obtained from the smackover formation limestone have low metal contents that are more typical of oil field waters but have very high concentrations up to 85 mg l of h 2 s computations with the geochemical code solmineq 87 give the following results 1 both pb and zn are present predominantly as aqueous chloride complexes mainly as pbcl 4 2 and zncl 4 2 respectively 2 the concentrations of metals complexed with short chained aliphatic acid anions and reduced s species are minor 3 organic acid anions are important in controlling the concentrations of metals because they affect the ph and buffer capacity of the waters at subsurface conditions and 4 galena and sphalerite solubilities control the concentrations of pb and zn in these waters

a reconnaissance study by paleomagnetic methods of the age of mineralization along the viburnum trend southeast missouri the mississippi valley type lead zinc ores of the viburnum trend in southeast missouri are hosted by the upper cambrian bonneterre dolostone the ore deposits are clearly epigenetic but conventional geologic and geochemical methods have failed to give an absolute date for the time of mineralization and thus have hampered the understanding of the ore genesis the magnetic remanences of both ore and host are very weak but measurable the paleopoles determined from the ore samples indicate an early permian late pennsylvanian magnetic event the host rocks collected in the mines have been remagnetized showing paleopole positions similar to those of the ore samples correlative bonneterre dolostone samples collected far away from mineralization have poles quite different from those of similar host rocks in the mine they probably still retain part of the original direction acquired during their sedimentation to explain all of the paleomagnetic results in this study best a mechanism for resetting the paleomagnetic clock by the mineralization is proposed according to this mechanism the age of the magnetic event observed from the rocks in the mine would probably represent the time of the mineralization if this premise is accepted the mineralization in the viburnum trend occurred in early permian late pennsylvanian time the paleomagnetic methods used are regarded as being potentially applicable to many other problems of a stratigraphic and diagenetic nature with the arrival of cryogenic magnetometers for routine usage paleomagnetic studies of many additional deposit types will have come of age

limist on the metal content of fluid inclusions in gangue minerals from the viburnum trend southeast missouri determined by laser ablation icp ms the hydrothermal fluids that deposited the ores of the viburnum trend of the southeast missouri district have long been recognized to be sedimentary basinal brines the major element composition of these brines has been well characterized however there have been no attempts to measure their metal content which is only loosely constrained by theoretical solubility relations the present study is an effort to assess the metal content of these mineralizing brines by analyzing fluid inclusions from gangue minerals in the viburnum trend using laser ablation inductively coupled plasma mass spectrometry la icp ms and microthermometry by focusing on gangue minerals instead of metal sulfide minerals interferences from the mineral matrix are avoided a high priority was to determine whether brines of anomalously high metal content were circulating through southeast missouri during the time of mississippi valley type mineralization fluid inclusions in dolomite quartz and calcite gangue from throughout the viburnum trend and representative of the entire paragenesis were analyzed none of the inclusions contained measurable quantities of pb zn or cu and only a few contained measurable quantities of ba which ranged from about 100 to 500 ppm where detection limits were not exceeded they indicated maximum possible concentrations of the element in the fluid inclusion maximum possible concentrations varied from inclusion to inclusion and were controlled by the mass of analyte within the fluid volume the larger or more saline the inclusion the lower the detection limit these results showed that the fluid that deposited quartz calcite and most of the dolomite gangue in the viburnum trend is unlikely to have had order of magnitude concentrations of pb and zn higher than 102 ppm or order of magnitude concentrations of cu higher than 101 ppm concentrations of pb and zn during deposition of stage 3 dolomite could not have been higher than 103 ppm and concentrations of cu could not have been higher than 102 ppm these upper limits on possible metal concentrations with the principal exception of those in stage 3 dolomite fluid inclusions are of magnitude similar to the highest measured concentrations of pb zn cu and ba found in typical sedimentary brines thus the brines responsible for depositing gangue minerals in the viburnum trend are unlikely to have had higher ore metal concentrations than typical basinal brines the lack of temporal overlap between gangue and metal sulfide deposition and the higher k na and lower ca mg ratios in fluid inclusions in the gangue minerals compared with fluid inclusions in the metal sulfides leaves open the possibility that the metal content of the fluid that deposited the sulfides was different from that responsible for depositing gangue however the data show that fluid entering the southeast missouri district was not pervasively metal rich throughout time and that if metal enriched fluid ever entered the district it did so at discrete intervals

low frequency modes of tropical ocean dynamics abstract basinwide very low frequency vlf modes with zonal uniformly deepening and shoaling of the equatorial thermocline are found as solutions of linear shallow water equations with the meridional basin boundaries under an equatorial plane they can be understood as the free heat content recharge oscillations the interannual vlf modes had been recognized as the essential part of the coupled recharge oscillator theory for the el nino southern oscillation it is suggested that the decadal vlf modes may also be transformed into coupled modes relevant to the pacific decadal climate variability through the ocean atmosphere interaction in the tropics

periglacial features on the margins of a receding plateau ice cap lyngen north norway some features around the perimeter of the balgesvarri plateau ice cap are described sorted stone circles were found beneath a slowly retreating ice margin the basal ice in this area appears to be below the pressure melting point no absolute dating of features was possible but a relative chronology is suggested resume le retrait glaciaire et les manifestations piriglaciaires sur les marges d un glacier de calotte a lyngen norvege du nord on decrit quelques traits caracteristiques du pourtour du glacier de calotte de balgesvarri des sols polygonaux ont ete decouverts a l aval d un front glaciaire en leger retrait la glace de fond dans cette zone semble ttre en dessous du point de fusion correspondant a la pression il n a pas ete possible d etablir une datation absolue de ces manifestations periglaciaires mais on propose une chronologie relative zusammenfassung gletscherriickgang und periglaziale erscheinungen an den riindern einer plateau eiskappe lyngen nordnorwegen einige erscheinungen an der peripherie der balgesvarri plateaukappe werden beschrieben unter einem langsam zuruckgehenden eisrand wurden steinkreise gefunden das eis am untergrund dieser region durfte si ch unter dem druckschmelzpunkt befinden eine absolute datierung der erscheinungen war nicht moglich doch llisst sich eine relative zeitliche abfolge ermitteln

the simplest enso recharge oscillator 1 eastern pacific sea surface temperature sst and mean equatorial pacific thermocline depth are key variables in el nino southern oscillation enso a linear fit to observations leads to a remarkably simple picture enso can be represented by a classical damped oscillator with sst and thermocline depth playing the roles of momentum and position respectively an independent fit of observed relationships between western and eastern thermocline depth central wind stress and eastern pacific sst yields the same picture and supports a recharge oscillator interpretation the oscillation arises from the interaction between the recharge time of the warm pool and the time delay between east and west pacific both finite kelvin wave speed and sst dynamics contribute to the time delay including seasonality in the description we find two periods of relative instability boreal spring with a large phase progression and autumn with nearly stationary phase

late paleozoic magnetization of mineralized and unmineralized ordovician carbonates from east tennessee evidence for a post ore chemical event thermal demagnetization studies on samples from mineralized and unmineralized rocks in the lower ordovician knox group of east tennessee reveal a mean direction of d i 157 18 95 7 7 k 52 9 after 60 unfolding combining stable endpoint and remagnetization circle data although not significant at the 95 confidence level the fold test is suggestive of a synfolding alleghenian age of the magnetization the magnetization cannot be postfolding i e permian or younger because the in situ directions do not resemble those for post carboniferous times the magnetization is unlikely to be much older than the folding because the directions with respect to bedding yield a paleopole characteristic of the early permian but unlike poles for pre late carboniferous times characteristic magnetizations from mineralized and unmineralized collapse breccias are in good agreement and fail the conglomerate test the best estimate for the paleopole resulting from this study falls at 40 n 126 e within the late carboniferous segment of the north american paleozoic apparent polar wander path thus the magnetization is interpreted as synfolding and secondary due to widespread kiaman remagnetization blocking temperatures of up to 520 c and the acquisition of isothermal remanent magnetization suggest magnetite as the carrier of the magnetization scanning electron microscopy and energy dispersive analysis of magnetic extracts from limestone samples reveal abundant magnetite spheres secondary dolomites have the same magnetic characteristics as the primary limestones and it is inferred that similar magnetite spheres are the carriers of their magnetization because this magnetization and therefore its carrier occurs in sphalerite and secondary dolomite it must be coeval with or younger than the ore which itself is thought to be of middle to late paleozoic age it is argued that the magnetization was acquired during growth of magnetite associated with a late paleozoic chemical event

periglacial geomorphology of the appalachian highlands and interior highlands south of the glacial border a review abstract many features reported in the appalachian region have been assigned a paleoperiglacial origin based on field relationships and their similarities with analogs active in present day actuoperiglacial environments these forms include but are not limited to sorted and nonsorted varieties of patterned ground grezes litees block fields block slopes and block streams cryoplanation terraces and hillslope and river terrace landscapes although very small scale features generally less than 1 m in plan or section dimension and some larger forms on steep hillslopes are known to be at least sporadically active today the large scale features discussed here are interpreted as either inactive or truly fossil periglacial phenomena thus they hav implications for paleoclimatic reconstruction and significance as indicators of relative landscape stability since the time s of their development this paper briefly reviews the historical dimension of early researchs work present selected examples of recent results and gives authors conclusions

sensitivity of an intermediate ocean atmosphere coupled model of the tropical pacific to its oceanic vertical structure an intermediate ocean atmosphere coupled model icm of the tropical pacific is used to investigate the sensitivity of the coupled system to the oceanic vertical structure the model consists of a three baroclinicmode tropical pacific ocean and a gill tropical atmosphere the mixed layer is similar to the zebiak and cane zc coupled atmosphere ocean model but uses a different parameterization for subsurface temperature derived from xbt data a 100 yr simulation is made and the long term variability of the icm is briefly discussed and compared with the the observations and the zc model the icm reproduces regular enso events with a spectrum peak centered at the period 3 5 yr the presence of higher order vertical modes in the oceanic component of the model allows for reduced off equatorial variability of zonal current and thermocline anomalies and for finer meridional scale for sst anomaly variability in comparison with a simulation with one baroclinic mode only the nature of the processes sustaining the oscillations in the icm is then investigated based on the coupled instabilities and delayed oscillator theories it

cation study of fluid inclusion decrepitates in the jubilee and gays river canada zn pb deposits characterization of ore forming brines an sem eds instrument sensitive to c and o is used to measure cation ratios in individual fluid inclusion decrepitates of main paragenetic phases from two nova scotian mississippi valley type deposits the technique confirms that the analyses obtained for the carbonate hosts are not contaminated by substrate and permits measurements of small amounts of decrepitates the technique has been used to investigate fluid compositions in inclusions of presulfide stage dolomite and calcite sulfide stage sphalerite and calcites and postsulfide calcite at the gays river and jubilee zn pb deposits in nova scotia the results indicate that na and ca are the two major cations minor amounts of k and mg are also detected nacl and cacl 2 ranges for decrepitates from the two deposits are as broad as for modem mixed brines and thereby suggest that solution mixing partly controlled the paleobrine compositions when compared to other mississippi valley type deposits the gays river and jubilee deposits are similar in nacl cacl 2 kcl composition to a group of mississippi valley type districts including deposits from the ozark region that are associated with large volume clastic sequences or paleoaquifers higher proportions of kcl at gays river and higher proportions of cacl 2 at jubilee indicate that the mineralizing brines interacted with horton group clastic aquifers of different mineral compositions the brines in the two areas might have originated from evaporation of seawater but they were later modified by interaction with clastic rocks of different compositions

properties of a chronosequence of ultraxerous soils in the trans antarctic mountains cold desert soils were examined on 27 lateral moraines and on ground moraine in arena valley antarctica 77 50 s 161 e the soils range in age from 200 000 to possibly 7 10 m y and have formed under virtually abiotic conditions currently receiving less than 1 cm of water equivalent precipitation per year on 314 m2 circular plots the frequency of surface boulders decreases and the frequencies of ventifacted boulders and pitted dolerite boulders increase with time the desert pavement becomes more distinct with time as manifested by an increase in rock types resistant to weathering proximity of fragments greater than 15 mm and number of coarse fragments which are stained and ventifacted the thickness of solum and depth at which comminuted clasts occur increase with time whereas salt encrustations beneath clasts are prevalent in the youngest soils the oldest soils contain a weakly cemented salt pan cracks measuring 1 5 cm intwidth irregularly spaced at 15 50 cm intervals and extending to depths of 50 cm occur primarily in older ultraxerous soils electrical conductivity and concentrations of sodium and nitrate in water extracts of the salt enriched horizon increase with time concentrations of cations in water extracts are ranked na ca2 mg2 k whereas anions are ranked no3 so42 cl in the upper part of the solumn the amount of gravel 76 2 mm decreases and the amounts of silt 20 2 m and clay 2 m increase with time the proportions of quartz and mica the dominant minerals in the clay size fraction increase with time lesser amounts of vermiculite montmorillonite and interstratified chlorite vermiculite and mica montmorillonite occur in the clay fraction

reactive flow models of ore formation in the southeast missouri district two dimensional numerical reactive transport modeling was used to investigate the deposition of pb zn cu ores in the southeast missouri district central united states by two potential mechanisms cooling of a fluid carrying metals and reduced sulfur and mixing of two fluids one enriched in metals but poor in sulfur and the other enriched in reduced sulfur but poor in metals the mechanisms were studied within the context of the topography driven ground water flow regime established in the ozark region by the late paleozoic alleghanian orogeny the models integrated geology fluid flow heat and solute transport and chemical reaction generating the most complete depiction yet of potential ore forming processes in southeast missouri both mechanisms were found capable of generating important characteristics of the mineralization patterns observed in the field but fell short in other respects in models of the cooling hypothesis mineralization was indeed found to be concentrated within the southeast missouri portion of the ozark region this was primarily because of the fact that mineralizing fluid underwent very little temperature change as it traversed the ozark region until it arrived in southeast missouri where its temperature decreased significantly the important association of mineralization with local basement highs within the southeast missouri district was also produced caused by local increases of fluid velocity over the crests of the basement highs smaller scale models however revealed much of the mineralization to be concentrated within the basal lamotte sandstone rather than the overlying bonneterre dolomite where it is actually concentrated in the field this model result stemmed directly from the fact that permeability and therefore fluid velocities were higher in the lamotte than in the bonneterre a further discrepancy with field observations was the high predicted concentrations of quartz which exceeded those of galena by over two orders of magnitude models of the mixing hypothesis also led to the regional concentration of mineralization in southeast missouri provided vertical dispersivities in the lamotte sandstone and bonneterre dolomite the formations that transmitted the two different types of fluids were low when dispersivities were high mineralization was produced more uniformly along the flow path in further conformity with field observations ore was concentrated in the bonneterre dolomite and particularly around the basement highs demonstrating the importance of the lamotte pinch outs in causing the fluids to mix the models reproduced well the observed vertical zonation in metals which was controlled by the relative solubility differences among the primary sulfide ore minerals however though mixing was induced by the configuration of the local geology its intensity was relatively low leading to ore grades that were considerably less than would be expected from geochemical grounds alone because the flow regime is predominantly laminar the two fluids tended to miscibly displace one another rather than vigorously mix with one another while still potentially a viable ore forming mechanism under conditions of high local dispersivity high dissolved metal and sulfur concentrations or high fluid velocity the mixing hypothesis as typically formulated in southeast missouri is nonetheless much less efficient than previously supposed greater efficiency could possibly be generated by reaction of aqueous species with solid phases in the matrix or gas e g h 2 s being generated in the matrix

fluid inclusion evidence for solution mixing sweetwater mississippi valley type district tennessee fluid inclusions in fluorite from the appalachian mississippi valley type fluorite barite deposits of the sweetwater district in east tennessee indicate that the mineralizing solutions were sodium potassium chloride brines with an average temperature of 107 degrees c and an average salinity of about 16 equiv wt percent nacl a strong negative correlation of homogenization and freezing temperatures which was observed for inclusions from the southeast part of the district was interpreted to indicate that two solutions were present during fluorite deposition in this area a warm 160 degrees c less saline 12 solution and a cool 80 degrees c more saline 30 solution a connate source is considered likely for both solutions and the warm less saline solution appears to have come from at or beyond the east edge of the district mixing of these solutions could have caused ore deposition in the southeast belt although cooling probably caused deposition elsewhere in the district published data suggest that two similarly distinct solutions were present in the nearby east tennessee zinc district

thermal regime and geomorphology of plateau ice caps in northern norway observations and implications the ice caps on high plateaus of northern norway lat 70 n can be grouped according to altitude the highest ice caps 1500m are dry based and are slowly retreating to reveal undisturbed block fields they appear to be found only in southern lyngen ice on plateaus at lower elevations 1500 m above sea level is wet based and has produced extensive striated bedrock surfaces and moraine sequences on the glacier forefields we propose that this geomorphological distinction can be applied to other plateau glaciers to identify present and in particular former basal thermal regimes

observed equatorial rossby waves and enso related warm water volume changes in the equatorial pacific ocean 1 modifications of the volume of warm water above the thermocline in the equatorial pacific are thought to be critical for enso el nino southern oscillation preconditioning development and prediction in this paper changes in this warm water volume wwv are first reviewed from the literature and then analyzed within 5 n 5 s in using 1992 2006 altimeter derived sea level anomalies sla and in situ observations we conclude that the 1992 2006 wwv changes in the equatorial band are a residual from the opposite effects of zonally integrated meridional ekman and geostrophic transports of warm water the latter being estimated from sla and validated against in situ observations for the first time with observations we evidence first baroclinic first meridional mode equatorial rossby waves to be responsible for the anomalous meridional geostrophic transports of warm water in changing the basin scale zonal pressure gradient these transports appear in phase opposition and proportional to the anomalous sea surface temperature sst in the region nino3 4 170 w 120 w 5 n 5 s the links between our observational results and the recharge discharge oscillator theory the differences in wwv between enso events and the hint for possible recent changes in the relation between wwv and nino3 4 sst are discussed

hydrothermal iron oxide cu au iocg mineralization at the jalal abad deposit northwestern zarand iran abstract the jalal abad iron oxide cu au bi co deposit is hosted in early cambrian volcanosedimentary units cvsu of the kashmar kerman zone central iran magnetite is the main ore mineral at depth and is associated with na ca rich alteration dominated by actinolite magnetite compositions epma are very low in tio2 0 03 0 07 wt v2o3 0 02 0 06 wt and coo 0 01 to 0 42 wt at intermediate to shallow levels potassic alteration is associated with chalcopyrite pyrite arsenopyrite cobaltite bismuthinite and gold the mineralization occurs in massive breccia matrix open space filling disseminated and vein like styles gold occurs as small inclusions

constraints from fluid inclusion compositions on the origin of mississippi valley type mineralization in the illinois kentucky district fluid inclusions hosted by mississippi valley type mvt ores in the illinois kentucky district were analyzed using microthermometry laser ablation inductively coupled plasma mass spectrometry la icp ms and raman spectroscopy to characterize the composition and temperature of mineralizing fluids in order to seek insights into the process of ore formation results from the present study support the interpretation of previous microthermometry studies that relate mineralization to mixing of two higher temperature brines and a cooler dilute meteoric fluid fluid inclusions in the illinois kentucky district have overall higher atomic ratios of ba na ca mg k na sr na and lower atomic ratios of mg na compared to inclusions in the ozark mvt districts and are thus compositionally distinct these differences may indicate that the illinois kentucky and ozark mvt ore fluids were derived largely from different source basins or may reflect input from igneous rocks in the illinois kentucky district low ca mg ratios of illinois kentucky fluid inclusions indicate that mineralizing fluids were dolomitizing and therefore could not have traveled far through the limestone ore host formations but instead traveled through deeper nonlimestone units before rising along faults and fractures in the district some fluid inclusions in illinois kentucky mvt mineralization yielded strong la icp ms responses for ore metals a single sphalerite hosted fluid inclusion out of 18 analyzed contained detectable pb corresponding to a concentration of 420 ppm whereas numerous fluorite hosted fluid inclusions contained detectable pb zn and cu corresponding to maximum concentrations on the order of 1 000s of ppm the high and similar concentrations of cu pb and zn in some fluorite hosted fluid inclusions in the illinois kentucky district are problematic because cu sulfide mineralization should be much more abundant than pb and zn sulfide mineralization owing to the lower solubility of cu relative to pb and zn in the presence of reduced sulfur which is not observed in the field this raises the possibility that ore metals may exist as solid phases in suspension or adhering to fluid inclusion walls in some inclusions rather than as dissolved species in aqueous solution raman microprobe analyses of fluid inclusions hosted by minerals occurring throughout the paragenetic sequence detected methane concentrations ranging from about 40 to 1 200 ppm with most on the order of 100s ppm even for the lowest methane concentration determined redox conditions would have been reducing at a log of 55 4 at a temperature of 100 c at such reducing conditions sulfide would predominate over sulfate this is supported by high concentrations of ba in the fluid inclusions the overall reducing conditions throughout the paragenetic sequence and the possible presence of both metal poor and rich fluid inclusions would suggest that mixing between a metal rich sulfide poor fluid and a metal poor sulfide rich fluid were an important mechanism for sulfide mineral precipitation minimum depths of mineralization estimated from methane concentrations in fluid inclusions range to about 1 500 m and possibly 2 500 m which would not have been reached until late pennsylvanian to permian time i e during the alleghanian orogeny

fault controlled alpine topography in norway abstract alpine topography in norway is largely fault controlled linear and asymmetric ranges developed in the footwalls of normal faults that were reactivated after the main phase of mesozoic rifting but prior to the late cenozoic glaciations stark geomorphological contrasts developed across the faults reflecting differential glacial exploitation of the pre glacial drainage pattern alpine topography developed preferentially in the footwalls triangular facets mark the traces of the most recently active faults at the base of deeply incised alpine range front escarpments the best exposed faults display metres thick fault rock successions and record multiple phases of fault movement juxtaposition of precambrian and caledonian basement rocks with jurassic or cretaceous sedimentary rocks provides evidence for fault activity in or after the mesozoic for some of the faults late cretaceous or younger reactivation is indicated by jumps in apatite fission track apparent ages across the faults and interferometric synthetic aperture radar and earthquake data attest to normal faulting at the present day two of the areas described host anomalous clusters of rockslides that may relate to tectonic activity the most distinct landscape forming faults in western scandinavia were probably active in the cenozoic and imposed asymmetric landscape patterns from the scale of single mountain ranges to the whole of scandinavia

wind stress curl and enso discharge recharge in the equatorial pacific discharge and recharge of the warm water volume wwv above the 20 c isotherm in an equatorial pacific ocean box extending across the pacific from 156 e to the eastern ocean boundary between latitudes 5 s and 5 n are key variables in enso dynamics a formula linking wwv anomalies zonally integrated wind stress curl anomalies along the northern and southern edges of the box and flow into the western end of the box is derived and tested using monthly data since 1993 consistent with previous work a wwv balance can only be achieved if the 20 c isotherm surface is not a material surface that is warm water can pass through it for example during el nino part of the wwv anomaly entering the box is cooled so that it is less than 20 c and therefore passes out of the bottom of the box the 20 c isotherm surface the observations suggest that the anomalous volume passing through the 20 c isotherm is approximately the same as t the anomalous wwv entering the western end of the box therefore the observed wwv anomaly can be regarded as being driven by the anomalous wind stress curl along the northern and southern edges of the box the curl anomaly changes the wwv both by divergent meridional flow at the edges of the box and vortex stretching that is the sverdrup balance does not hold in the upper ocean a typical amplitude for the rate of change of wwv for the 5 s 5 n box is 9 6 sv sv 10 6 m 3 s 1 the wind stress curl anomaly and the transport anomaly into the western end of the box are highly correlated with the el nino index nino 3 4 the average sea surface temperature anomaly ssta over the region 5 s 5 n 170 120 w and nino 3 4 leads minus the wwv anomaly by one quarter of a cycle based on the preceding results a simple discharge recharge coupled enso model is derived only water warmer than about 27 5 28 c can give rise to deep atmospheric convection so unlike past discharge recharge oscillator models the west central rather than eastern equatorial sstas are emphasized the model consists of two variables t the ssta averaged over the region of strong enso air sea interaction in the west central pacific equatorial strip 5 s 5 n 156 e 140 w and d the 20 c isotherm depth anomaly averaged over the

a pennsylvanian paleomagnetic pole from the mineralized late cambrian bonneterre formation southeast missouri one hundred eighty eight oriented samples of the late cambrian bonneterre carbonates of southeastern missouri were taken from viburnum trend mines and local surface outcrops initial natural remanent magnetization directions have south southeasterly declinations and downward inclinations progressive demagnetizations using thermal and af techniques give two directions one is a viscous present day field direction and the other is of reversed polarity with south southeasterly declinations and very shallow inclinations the resulting paleopole at 43 n 126 e is located near the pennsylvanian to early permian segment of the north american apparent polar wander path a negative conglomerate test supports this assignment for the magnetization age magnetic extracts from the mineralized as well as unmineralized zones of the bonneterre contain spherical crystal aggregates of pure magnetite of late diagenetic origin the secondary magnetization resides in the magnetite spheroids and we infer that the spheroids formed prior to sulfide mineralization

weathering patterns in high latitude regolith 1 large areas distributed on the earth s surface are covered by regolith an unconsolidated heterogeneous material overlying bedrock in high latitude areas most of the land surface has been reworked and eroded by both glacial and fluvial processes leaving only remnants of formerly extensive regolith covers in an effort to further the understanding of weathering patterns and processes in old regolith covers a comprehensive study of localities spread across norway was carried out on the basis of the distribution of minerals and elements within regolith as well as its internal structure and geomorphologic setting we ascertained that it was formed in situ and originated in pre quaternary times there are similarities between the study sites with respect to regolith thickness zonation and composition the chemical index of alteration cia and the weathering index of parker wip suggests that the degree of chemical weathering in the regolith is advanced compared to the parental bedrock with a maximum change of over 80 which indicates a substantial increase in the proportion of secondary versus primary minerals mineral analysis identified kaolinite and gibbsite which are considered indicative of advanced weathering and therefore support this observation on the basis of statistical relationships between different grain size fractions 125 m we observed a consistent pattern which revealed that physical weathering becomes progressively less important in the production of grains smaller than 32 m on the basis of this finding we infer that chemical weathering progressively dominates the production of fine silt very fine silt and clay whereas physical weathering primarily controls the production of grain size fractions larger than 32 m this particular pattern is suggested to be an intrinsic feature in the formation of weathered high latitude regolith

geochemistry and mineralogy of saprolite in finnish lapland abstract an ancient saprolite has developed on the palaeoproterozoic granulite granite gneiss and amphibolite bedrock of the vuotso tankavaara area of central finnish lapland the present day climatic regime in finnish lapland lies within the northern boreal zone and so the saprolite there can be regarded as fossil cores of saprolite were collected from 4 sections 42 samples and analyzed chemically and mineralogically in the study area progressive weathering of the rocks has been marked by gradual enrichment in al fe and ti and depletion of na k and ca the higher concentration of fe iii and water and reduced na and ca in weathered bedrock in the 4 sections are indicative of oxidation hydration and leaching processes involved during weathering the primary minerals in the saprolite are plagioclase feldspar k feldspar quartz garnet almandine and hornblende the common secondary minerals are kaolinite halloysite and vermiculite in addition to minor amounts of sericite intense weathering is indicated by 1 the presence of kaolinite and halloysite in 4 sections of different bedrock types and 2 the comparatively lower sio2 al2o3 wt ratio 2 30 of weathered granulites 3 sections as compared to fresh granulite 4 33 and that of weathered amphibolite 2 68 as compared to fresh amphibolite 3 56 in general kaolinite and halloysite have formed through the weathering of feldspars garnet and biotite vermiculite is the most probable alteration product of biotite the formation of kaolinite and halloysite in finnish lapland indicates wetter and warmer climatic conditions during the time of their formation than at present the possible time for formation of the saprolite is early cretaceous early tertiary into middle miocene

stable isotope and fluid inclusion studies of early zn cu ni co rich ores lower ore zone of brushy creek mine viburnum trend mvt district missouri u s a products of multiple sulfur sources and metal specific fluids abstract mississippi valley type mvt deposits of the viburnum trend are typically lead dominant and occur in the upper portion of the cambrian bonneterre dolomite unusual zinc and copper rich ores with notable enrichments in ni co and ag have been discovered within the lower bonneterre dolomite more than 30 m below the district s main ore bearing horizon these ores appear to be localized along fault fracture zones within the lamotte sandstone which promoted extreme dissolution of the base of the overlying bonneterre dolomite and resulted in pronounced vertical zoning of early ni co cu zn and pb ores above the sandstone dolomite contact stable isotope and fluid inclusion studies were undertaken to assess whether the deep ores resulted from a single fluid reservoir that evolved from cu ni co rich to zn rich to pb rich or are instead products of distinct fluids unrelated to the stratigraphically higher main pb rich ores of the district sphalerite hosted fluid inclusions from the lower orebody appear to be geochemically distinct from those that formed the upper orebodies they record the highest k na and mg na ratios in the southeast missouri mvt district suggesting dominance of siliceous lithologies arkose and or felsic igneous rocks over limestones along their ore fluid pathways paragenetic trends indicate that distinct fluid compositions are associated with specific generations of sphalerite which likely reflects the presence of multiple fluids the 34s values of ore minerals early pyrite and chalcopyrite 7 to 5 early sphalerite 6 to 15 main sphalerite 7 to 17 v cdt indicate deposition from fluids that utilized isotopically distinct sulfide reservoirs low 34s sulfur sources for early ores likely included sulfide in local brines within the lamotte sandstone and diagenetic sulfide minerals within the basal units of the bonneterre dolomite a trend of increasing 34s values of ore sulfides from 5 toward 17 with vertical distance above the lamotte sandstone bonneterre dolomite contact indicates that as the deep ore fluid system worked its way upward it breached less permeable units in the lower bonneterre dolomite allowing incorporation of high 34s sulfide from brines present higher in the stratigraphic section a concomitant up section pattern of decreasing 18o values of dolomite cement and recrystallized remnant host rock from 3 toward 9 v pdb is also consistent with a localized deep mineralizing fluid system which interacted progressively with the stratigraphically higher regional scale pb rich fluid system the episodic nature of metal sulfide deposition in the lower ore zone points to a system in which fluid mixing would have been highly variable both temporally and spatially reaction path models require mixing of multiple ore metal specific and sulfide bearing fluids in order to form the orebody the sequence and concentrations of metal sulfides are inconsistent with ore formation from a single evolving metal bearing fluid this study indicates that faults localized early metal and sulfide bearing fluids facilitating mixing of fluids that resulted in the accumulation of high grade ores near the bonneterre dolomite lamotte sandstone contact recognition of fault fracture patterns beneath more typical pb rich orebodies in the viburnum trend may be a viable exploration strategy for similar zn cu co ni rich deposits

a further investigation of the recharge oscillator paradigm for enso using a simple coupled model with the zonal mean and eddy separated the recharge oscillator paradigm for enso is further investigated by using a simple coupled model which externally includes the equatorial wave dynamics represented by the kelvin and gravest symmetric rossby waves to investigate the role of eddies in the pacific basin wide adjustment to the wind forcing particularly at the western and eastern boundaries the zonal mean and eddy parts are treated separately in the current model it is clearly demonstrated that the basin wide adjustment of the tropical ocean is accomplished by the net mass transport induced by the meridional transport over the tropical ocean interior and the zonal fluxes at the boundaries with a reasonable choice of the reflection coefficient particularly at the western boundary the meridional transport plays a bigger role than the zonal boundary flux and determines the sign of zonal mean thermocline depth tendency in a way that the discharge of equatorial mass in the warm phase and recharge in the cold phase serve as a phase transition mechanism of the coupled system the meridional mass transport is induced mainly by a geostrophic current associated with the east west slope of thermocline depth established quickly by the wind forcing also discussed in this paper is the difference between the recharge oscillator and the delayed oscillator in explaining the phase transition mechanism of enso

weathering mantles and their significance for geomorphological evolution of central and northern europe since the mesozoic abstract weathering mantles saprolites are very widespread in central western and northern europe where they form thick near surface residual deposits often in excess of 50 m they vary in the type of weathering the bedrock lithology involved the topographic setting and the age and stratigraphic context this review paper provides information about the distribution and major characteristics of weathering mantles from a number of key areas including the british isles the central european belt of mid mountains and uplands the scandinavian mountains and the fennoscandian shield it also examines the evidence for weathering etched origin of various landforms including boulders tors inselbergs basins and some regional landforms assemblages major types of regionally important weathering mantles include ferrallitic lateritic saprolites kaolinite rich saprolites sandy to grus mantles and various residuals left after partial dissolution of carbonate rocks although dating of weathering mantles is often circumstantial it appears sufficiently precise to argue for various ages of deep weathering mesozoic pre late cretaceous mantles are particularly widespread but there are also early tertiary and miocene saprolites widely present whilst most grus weathering is likely to be of miocene to pleistocene age individual upland areas have been subjected to multiple episodes of weathering whose legacy is the present day co existence of different weathering products continental and shallow marine deposits around the uplands particularly in the north sea and intra continental graben structures are often dominated by quartz and kaolinite pointing to deeply weathered land surfaces as the source areas and extending the record of weathering on the geological time scale they demonstrate that weathering mantles repeatedly formed and were subjected to erosion and new cycles of weathering were initiated we suggest that deep unroofing of basement structures in many parts of europe has been mainly accomplished by deep weathering and stripping of pre weathered rock the phenomenon of deep weathering has been very important for geomorphology etched landforms vary in size from small residual boulders up to regional characteristic landscapes etchsurfaces such as joint valley landscapes of southern sweden or undulating multi convex and multi concave landscapes of many uplands in central europe deep weathering has played a major part in the geomorphological evolution of europe since at least the late triassic and the concept involving long term etching and stripping provides an appropriate framework to describe and explain both erosional landscapes and sediment features

constraints on the origins of fluids forming irish zn pb ba deposits evidence from the composition of fluid inclusions the numerous zn pb deposits in the irish midlands together with the quantity and grade of the ore make this a world class base metal province despite significant exploration and research there is still disagreement on the origin of the mineralizing fluids in this study we have measured the composition of fluid inclusions using a crush leach technique these data constrain the possible sources of the fluids both during and after mineralization chloride and br concentrations indicate that the main ore fluid at tynagh and silvermines was seawater that had evaporated until the salinity was between 12 and 18 wt percent however na k and li data show that water rock interactions have resulted in the depletion of na and the enrichment of k and li relative to the concentrations expected for evaporated seawater the fluids that produced postore dolomitization were also derived from seawater that had evaporated to higher salinities and had precipitated halite the concentrations of na k and li are what would be expected for seawater at this degree of evaporation and show that these fluids did not interact with the same lithologies as the ore fluids the major change to their fluid composition was exchange of mg for ca during dolomitization we suggest that the ore fluids could only have reached their high salinity by evaporation of seawater on the extensive shallow water shelf regions that existed over much of the irish midlands

genetic implications of regional and temporal trends in ore fluid geochemistry of mississippi valley type deposits in the ozark region fluids extracted from aqueous fluid inclusions in epigenetic gangue and ore minerals record the migration of huge volumes of highly saline fluids throughout the stratigraphic section of the ozark region the extracted fluids share many similarities regionally but there are significant temporal differences which define two geochemically distinct end member ore forming fluids that we refer to as the viburnum trend main stage or viburnum trend type and the tri state type viburnum trend type fluids are enriched in potassium and are associated only with deposits close to the basal lamotte sandstone the main stage octahedral galena ore of the viburnum trend and much of the old lead belt ore is thought to be derived from this type of ore fluid galena deposited by viburnum trend type fluids contains less radiogenic lead than galena deposited by tri state type fluids sulfides deposited by viburnum trend type fluids also contain isotopically heavier sulfur and significant amounts of copper cobalt nickel and silver tri state type fluids have a low potassium content when compared with viburnum trend type fluids and are characteristic of deposits where ore forming fluids migrated through large volumes of carbonate rock these fluids are thought to have formed the ore deposits of the tri state northern arkansas and central missouri districts the cubic galena stage ore of the viburnum trend and the many trace occurrences of sphalerite throughout the ozark region galena deposited by tri state type fluids has more radiogenic lead and the sulfides have isotopically lighter sulfur than sulfides deposited by viburnum trend type fluids a systematic south to north increase of potassium in the tri state type fluids suggests that they migrated from a southerly source such as the arkoma basin possible explanations for the origins of these two end member fluids include 1 a single parent brine evolved into two distinct fluids due to reactions with geochemically distinct aquifers during migration 2 the two distinct fluids reflect normal fluid evolution within a single source basin of a bittern and of later halite dissolution and 3 the viburnum trend and tri state type brines migrated to southeast missouri from two different source basins our data does not preclude any of these possibilities however the geochemical similarity of the viburnum trend end member fluid to a bittern may be accounted for by water rock modifications of the brine during migration other evidence strongly supports a southerly source for the ore forming brines thus limiting possible sources for the viburnum trend type fluid to the arkoma and or black warrior basins of the ouachita foreland trough viburnum trend type fluid flow was probably funneled northward through basal sandstones within the reelfoot rift and water rock modifications occurring there may have resulted in its unique geochemistry

nacacl saline formation waters frio formation oligocene south texas usa products of diagenesis abstract saline formation waters from reservoirs in oligocene deltaic clastic sedimentary rocks frio formation south texas are derived from three sources mixtures characterize most samples accounting for the wide range in chemistry low salinity water is derived from cenozoic shales in contrast saline water having variable br cl ratios is allochthonous and is derived from at least two sources in mesozoic strata which underly the cenozoic units saline water in this area regardless of br cl ratio contains variable high concentrations of ca calcium is derived primarily from dissolution of plagioclase as demonstrated by petrography 87 sr 86 sr analyses and chemical modelling the mccl 2 or carpenter function of saline formation waters in this area thus can be derived from water rock interaction and cannot be used to identify the ultimate source of solutes reverse osmosis is an unimportant processes in this area and 18 o and d values converge on rock buffered values of approximately 8 o and 30 o respectively

composition of ore fluid inclusions from the viburnum trend southeast missouri district united states implications for transport and precipitation mechanisms fluid inclusions hosted by sphalerite and dolomite cement from the mississippi valley type mvt deposits of the viburnum trend of the southeast missouri district were analyzed by microthermometry and laser ablation inductively coupled plasma mass spectrometry la icp ms to determine the composition of mineralizing fluids and to seek insights into ore forming processes on the whole fluid inclusions from throughout the paragenesis have compositions resembling deep sedimentary brines a population of anomalously pb rich fluid inclusions with concentrations reaching 1 500 ppm was identified in some of the paragenetically early and main stage sphalerite which is interpreted to represent the influx of a pb and possibly overall metal rich fluid into southeast missouri during the time of sulfide mineralization this influx of pb rich fluid appears to have been intermittent as at least one stage of dolomite cement that hosts pb poor fluid inclusions occurs between intervals of sphalerite that host pb rich fluid inclusions if fluid flow into the district was principally from one direction for example from the arkoma basin to the south then the intermittency in high pb concentrations could be explained by compositional changes in the source region or along the flow path alternatively if fluid flow into the district was from two or more directions and fluid arriving from each direction had a different composition then the intermittency in high pb concentrations could be explained by transient variations in the relative flow rates from each direction lead concentrations on the order of thousands of parts per million make it unlikely that the southeast missouri ores were precipitated by any mechanism that involved simultaneous transport of metals and sulfide in the same fluid as the concentrations of sulfide that could coexist with such high concentrations of pb would be too low to allow the ores to be deposited within a geologically reasonable period of time unless the ph was very low or groundwater flow rates were very high thus some type of mixing scenario seems more likely involving either mixing of a metal with a sulfide rich fluid or mixing of a metal and sulfate rich fluid with a reductant present either in the host rock or in another fluid fluid inclusions hosted by sphalerite have k na and ca mg ratios that partly resemble the compositions of both main stage cuboctahedral galena and less abundant late stage cubic galena suggesting that sphalerite was precipitated from a mixture of the fluids that precipitated these two types of galena however the fact that aqueous pb concentration does not correlate with these ratios or other indicators of main stage mineralization such as matrix mn fe co cu ag and cd content in sphalerite suggests that more than two fluids were involved in mixing

preservation of landforms under ice sheets and ice caps abstract this article addresses the question of whether or not distinct glacial and non glacial landforms can survive beneath ice sheets and ice caps with little or no morphological alteration a review of recent work documents the existence of pre last stadial landforms and landscapes in areas covered by the fennoscandian and laurentide ice sheets a substantial number of independent works indicate that landforms such as eskers drainage channels and boulder fields have escaped destruction despite complete ice overriding during several tens of millenia full preservation of former ground surfaces or delicate landforms probably is linked to areas where the ice sheet base was continuously frozen to its bed larger robust landforms such as large drumlins appear to have been preserved even under wet based conditions in glaciated areas patches preserved under dry cold based conditions provide important windows towards the past showing landscapes that were destroyed in surrounding areas affected by wet based and eroding ice some consequences for the research fields of non glacial geomorphology archaeology and botany include the possibility of subglacial museums and refugia a time space model describes geomorphological access to information from older events in glaciated areas

analysis of a blockstream in the northern lesotho drakensberg southern africa abstract blockstreams are found in many mountain ranges worldwide and can be considered as an expression of the interplay between upslope sediment supply and transport limited capacity of slope sediment systems in mountain settings blockstreams have been most commonly described as periglacial landforms whose development and internal morphology reflect active layer processes and where the landforms are not active under present climatic conditions in the maloti drakensberg mountain range of eastern lesotho southern africa several blockstreams have been identified but their age evolution and relationships to climatic conditions are largely not known this study maps and analyses the properties of one large blockstream in the maloti drakensberg using field measurement techniques including schmidt hammer relative exposure age dating of blockstream boulders results show that the blockstream is a relict feature but debris may have been derived from several sources including from periglacial slope activity the presence of arcuate flow lobes within the main body of the studied blockstream attests to phases of slope driven boulder movement possibly controlled by active layer processes and cryoturbation or by slip at the base of the sediment body driven by seasonal water availability relative age data from schmidt hammer analysis suggest that different parts of the blockstream may have different ages and or sources by comparison with blockstreams elsewhere in the maloti drakensberg it is likely that it is of late quaternary and probably of local last glacial maximum age but younger holocene phases of activity cannot be excluded

stone runs in the falkland islands periglacial or tropical abstract stone runs is the falklands vernacular term for openwork boulder accumulations which include extensive blockstreams like the famous darwin stone river and associated features such as stone stripes since the early 20th century they have been interpreted as the product of a suite of periglacial processes including frost wedging gelifluction frost heave frost sorting and snowmelt runoff following a literature review the results of recent field investigations of the valley floor blockstreams of east falkland are presented access to the internal structure of these forms provides evidence for the existence of a three fold profile with clear vertical size gradation presenting striking similarities with an inverted weathering profile micromorphological analyses sem xrd thin sections and grain size analyses lead to the hypothesis of an alternative model of stone run formation it is suggested that the material forming the stone run profile lato sensu including the superficial pavement is not of periglacial origin but derives directly from the stripping and accumulation downslope of a regolith possibly tertiary in age and formed under subtropical or temperate conditions the valley floor stone runs should therefore be considered as complex polygenetic landforms that may have formed according to a six stage scenario including in situ chemical weathering regolith stripping by mass movements soil formation further regolith stripping downslope accumulation and matrix washing out all phases possibly achieved by the early quaternary periglacial reworking of the stone run material would have operated at a final stage i e during quaternary cold stages with boulder bioweathering and limonite staining operating during the temperate intervals including the present one the suggested antiquity of the falklands blockstreams is in accordance with caine s pioneer interpretation of tasmania blockfields and with recent analyses and cosmogenic datings of blockfields from scandinavia and north america

blockfields old or new evidence and implications from some plateaus in northern norway evidence is presented from investigations on plateau top blockfields in still glaciated regions of north norway pits dug into these blockfields typically show profile depths 0 5 m and sometimes in excess of 1 m analysis of fines shows enrichment in the silt and clay sized fraction suggestive of prolonged chemical weathering chemical alteration of parent material is supported by xrd analysis which identifies a number of clay minerals present in blockfield samples a chemical weathering origin suggests that these plateau top blockfields are features which have considerable longevity in the landscape and have been forming since perhaps tertiary times the original weathering profiles have been destroyed by frost heaving mechanisms protection of the blockfield by cold based ice occurred during periods of glacial coverage

ocean response to wind variations warm water volume and simple models of enso in the low frequency approximation abstract physical processes that control enso are relatively fast for instance it takes only several months for a kelvin wave to cross the pacific basin tk 2 months while rossby waves travel the same distance in about half a year compared to such short time scales the typical periodicity of el nino is much longer t 2 7 yr thus enso is fundamentally a low frequency phenomenon in the context of these faster processes here the author takes advantage of this fact and uses the smallness of the ratio ek tk t to expand solutions of the ocean shallow water equations into power series the actual parameter of expansion also includes the oceanic damping rate using such an expansion referred to here as the low frequency approximation the author relates thermocline depth anomalies to temperature variations in the eastern equatorial pacific via an explicit integral operator this allows a simplified formulation of enso dynamics based on an integro differential equation within this formulation

paleomagnetism and rock magnetism of the mississippian leadville carbonate formation and implications for the age of sub regional dolomitization the mississippian leadville formation of central colorado is dolomitized near the sawatch uplift and hosts numerous pb zn ag mineral deposits paleomagnetic and rock magnetic data from several dolomite types away from centers of tertiary intrusive activity imply a late paleozoic late mississippian age for the dolomitization e g d 148 i 11 k 86 95 8 6 n 3 localities 31 samples in dolomitized units the magnetization is of diagenetic origin and was probably acquired during or soon after dolomitization tertiary thermochemical activity has overprinted dolomites close to intrusive centers data indicate that limestones removed from igneous activity were also remagnetized at the same time

collective role of thermocline and zonal advective feedbacks in the enso mode the vertical advection of anomalous subsurface temperature by the mean upwelling and the zonal advection of mean sea surface temperature sst by anomalous current are known to be essential for the equatorial sst anomaly associated with the el nino southern oscillation enso in the coupled model these two processes are referred to as the thermocline feedback and the zonal advective feedback respectively using a version of a recharge oscillator model for enso obtained from the stripped down approximation of the cane zebiak type model it is demonstrated that these two feedbacks which are linked dynamically through the geostrophic approximation tend constructively to contribute to the growth and phase transition of enso however these two feedbacks control the leading coupled mode in different ways the thermocline feedback leads to a coupled mode through the merging of the damped sst mode and ocean adjustment mode whereas the zonal advective feedback tends to destabilize the gravest ocean basin mode with both of these feedbacks the leading modes of the coupled model still can be traced back to these different origins under moderate changes in the model setup the main consequence of these sensitivities is that the growth rate and frequency of the enso mode may be sensitive to slight changes in basic state parameters which control the strength of these feedbacks

glacial trimlines to identify former ice margins and subglacial thermal boundaries a review and classification scheme for trimline expression abstract reconstructions of former ice sheets and glaciers provide important palaeoglaciological information about their behaviour in response to climate changes glacial trimlines record both the margin positions and palaeo ice thickness enabling the production of empirically constrained 3 dimensional reconstructions however the literature review into the characteristics interpretation and use of glacial trimlines here presented shows that these features have been under utilised and are poorly described in the existing literature with a confusing terminology currently in use a new classification scheme and terminology for trimline identification and interpretation is developed to better facilitate further research into these common features of glacierised and formerly glaciated landscapes