al substituted goethite an indicator of pedogenic and other weathering environments in south africa abstract over 200 goethite containing samples from widely diverse environments along the eastern seaboard of south africa were examined and described mainly by x ray powder diffraction xrd aluminium substituted goethites ranging from 0 to about 32 mole alooh were identified mainly by xrd line shift and chemical extraction they occur in every soil zone and major soil type in one or other form from sources such as 1 non hydromorphic highly weathered strongly acid soils ferruginous bauxites saprolites and moderately weathered moderately acid soils environments 2 hydromorphic environments mottles concentrations pipe stems crusts ferricretes geodes and 3 crusts in calcareous environments these goethites formed in different climatic and weathering environments were grouped according to their amount of al substitution and crystallinity as determined by xrd line broadening al substitution in goethite formed in hydromorphic moderately acid soils and calcareous environments was generally low 0 15 mole goethite formed in non hydromorphic highly weathered environments was generally high in al substitution 15 32 mole and increased in the following order saprolites and strongly acid freely drained soils this study showed that the degree of al substitution and crystallinity of goethites may reflect the environment in which they have formed and serve as an indicator of soilforming processes

red mediterranean soils in jordan new insights in their origin genesis and role as environmental archives it is disputed whether terrae rossae form mainly out of the bedrock residue from allochthonous material like aerosols or by isovolumetric replacement furthermore whether they are mainly relic soils or are still forming is subject to debate these questions were addressed by comparing the geochemistry of several limestone and basalt based red mediterranean soils with lithosols on sandstone and limestone in jordan the bedrock residue was included at all test sites paleosols and initial soils on the limestone regolith of historic ruins delivered insights into the possible time frame of soil development a major reduction of elements in the soils compared to bedrock could be observed for cao in carbonaceous sio2 in arenaceous and fe2o3 and mgo in basaltic rocks all terrae rossae however are characterised by a significant increase of sio2 al2o3 tio2 fe2o3 k2o and a range of mainly metallic minor elements that cannot be derived from the bedrock a reasonable explanation could be input via aeolian transfer of minerals with clay minerals as the major carrier plus quartz this input probably originates in egypt and sudan and has remained largely unchanged over long periods growing aridity during the holocene has apparently increased the share of silt while clay deposition and soil development has been reduced at some sites metasomatic processes have contributed to soil development and might help to explain the depth of some profiles however formation of red soils during the holocene seems very limited and the red mediterranean soils may represent remains of a paleolandscape

estimating relative ages from iron oxide total iron ratios of soils in the western po valley italy abstract nineteen samples were collected from deeper layers of as many terraces forming agesequences in five basins most samples were collected at depths of 1 m or more with some below 3 m soils at the sample sites were tentatively identified as alfisols entisols or inceptisols total amounts of iron and the amounts extractable by dithionite and by oxalate were determined for the 19 samples redness ratings were calculated from sample colors and related to amounts of extractable iron by regression mineralogies of the fine sand silt and clay fractions were also determined the percentage of the total iron fe t extracted by dithionite fe d minus the amount extracted by oxalate fe o increased gradually with ages of the terraces which range from early middle pleistocene to upper pleistocene holocene these percentages are independent of the total amounts of iron in the samples and of the general lithology of a basin such ratios thus promise to be useful in estimating relative ages especially where time sequences exist mineralogies of the samples were consistent with relative ages of terraces as estimated from the ratios of iron in different forms so were the redness ratings the regression of extracted iron on redness ratings suggests that colors can be used as preliminary field indicators of relative ages of terraces without time sequences

the red soils their origin properties use and management in greece abstract red soils in greece are distributed thoughout the country but they occur more frequently in the southern provinces and constitute important soil resources supporting several land utilization types they can be grouped into two categories the autochthonous and the allochthonous the former soils are found on hard limestone and on basic igneous rocks in sloping mountainous or hilly landscapes moreover they can be found on mica schists and gneisses in locations adjacent to marble or calcareous mica schists allochthonous red soils are wide spread on late tertiary and pleistocene surfaces in the lowlands many of these deep deposits have red strata a few decimeters to several meters thick or red colored and fine textured layers interbedded with light colored deposits of marl or conglomernates and also with thick strata enriched with calcareous concretions they are distributed in the thermo and meso mediterranean bioclimatic zones these sites have a common feature the gently sloping terrain that ensures efficient drainage there are some differences in chemical and physical properties and in the clay mineralogy of the two groups of greek red soils palygorskite is present in some soils developed on basic rocks the clay minerals of the allochthonous soils on pleistocene and late pliocene seems to be mixed with micas in significant amounts soil forming factors required for the formation of red soils are a parent material containing iron bearing minerals and rich in bases b slope gradients and or water permeabilities of the bed rock securring excessive drainage and c vegetation cover that does not produce high amounts of and deeply distributed organic matter the allochthonous red soils have likely inherited their color from their parent materials that were transported from the originally formed residual soils on hard limestone the soils retain the red color in the thermo mediterranean zone only on sloping terrains the soils on these landscapes are frequently stratified the greek red soils belong to the great groups of rhodoxeralfs palexeralfs xerochrepts orthents large portions of the allochthnous soils have been desertified or have been severely degraded and their extensive exploitation is not recommended soil management practices applied in the allochthnous soils include erosion control preservation of organic matter minimum tillage split application of nitrogen using non acidifying fertilizers irrigation soil water conservation and sheltered agriculture

geochemistry of laterites stability of al goethite al hematite and fe super 3 kaolinite in bauxites and ferricretes an approach to the mechanism of concretion formation

late glacial stage and holocene tropical ice core records from huascaran peru two ice cores from the col of huascaran in the north central andes of peru contain a paleoclimatic history extending well into the wisconsinan wurm glacial stage and include evidence of the younger dryas cool phase glacial stage conditions at high elevations in the tropics appear to have been as much as 8 to 12 c cooler than today the atmosphere contained about 200 times as much dust and the amazon basin forest cover may have been much less extensive differences in both the oxygen isotope ratio 18o 8 per mil and the deuterium excess 4 5 per mil from the late glacial stage to the holocene are comparable with polar ice core records these data imply that the tropical atlantic was possibly 5 to 6 c cooler during the late glacial stage that the climate was warmest from 8400 to 5200 years before present and that it cooled gradually culminating with the little ice age 200 to 500 years before present a strong warming has dominated the last two centuries

discharge of debris from ice at the margin of the greenland ice sheet sediment production at a terrestrial section of the ice sheet margin in west greenland is dominated by debris released through the basal ice layer the debris flux through the basal ice at the margin is estimated to be 12 45 m 3 m 1 a 1 this is three orders of magnitude higher than that previously reported for east antarctica an order of magnitude higher than sites reported from in norway iceland and switzerland but an order of magnitude lower than values previously reported from tidewater glaciers in alaska and other high rate environments such as surging glaciers at our site only negligible amounts of debris are released through englacial supraglacial or subglacial sediment transfer glaciofluvial sediment production is highly localized and long sections of the ice sheet margin receive no sediment from glaciofluvial sources these findings differ from those of studies at more temperate glacial settings where glaciofluvial routes are dominant and basal ice contributes only a minor percentage of the debris released at the margin these data on debris flux through the terrestrial margin of an outlet glacier contribute to our limited knowledge of debris production from the greenland ice sheet

the iron content of some red mediterranean soils from northeast spain and its pedogenic significance abstract alfisols cover 18 of the surface of the ne edge of the garraf massif se of barcelona catalonia most of these are mediterranean red soils some representative pedons especially over mesozoic limestones are discussed in this paper climate of the zone is littoral mediterranean mean temperature 16 c precipitation 650 mm pedoclimatic regimes are xeric and thermic vegetation is quercetum ilicis galloprovinciale horizon b is 5yr and 2 5yr in munsell hue with a phw of 7 2 to 8 6 all of them are base saturated and the majority recarbonated organic matter content is 2 5 some have an isohumic character the illuviation clay index ranges from 0 37 to 0 87 and the mean value of the illuviation fe index is 0 76 the nearly constant fed clay ratio indicates co illuviation values for fed are between 0 40 and 2 81 the mean feo is 0 057 and it ranges between 0 to 0 14 generally redness rating rr increases with fed values of fed fe1 vary from 0 22 to 0 82 and the mean is 0 54 rubefaction according to redness rating is moderate taxonomically calcic haploxeralfs predominate and are located at 50 70 m above sea level calcic palexeralfs at 70 80 m and again at 150 m and petrocalcic palexeralfs at 80 130 m are also found typic haploxeralfs are frequent over limestones at higher altitudes 260 m or overlying silicic rocks found at 35 65 m according to the 1967 french classification system they are red fersialitic and brown fersialitic soils and some are integrades with cinnamotnic soils marron encroute

mineral chemical studies of metamorphosed hydrothermal alteration in the kristineberg volcanogenic massive sulfide district sweden the massive sulfide deposits of the kristineberg area sweden occur within a 2 to 3 km thick succession of felsic volcaniclastic rocks belonging to the skellefte group the volcanic pile is intruded by a synvolcanic jorn type granitoid viterliden intrusive complex and is overlain by a thick sequence of metasedimentary rocks vargfors group mineralization occurs at two main stratigraphic levels at the base of the felsic volcanic succession and at the contact with the metasedimentary rocks of the vargfors group the kristineberg cu zn mine is the largest deposit approximately 21 mt and occurs at the base of the volcanic pile close to the contact with the viterliden intrusive complex four smaller deposits ravliden ravlidmyran horntrask and nyliden occur along the upper ore horizon these deposits are thought to be related to a late intrusive phase of the viterliden complex which cuts the altered volcanic rocks at the kristineberg deposit within an area of about 50 km2 surrounding the kristineberg deposit felsic volcanic rocks between the two ore horizons are affected by extensive albite destructive alteration sodium depletion and development of chlorite and muscovite strong co enrichment in magnesium and potassium the kristineberg deposit is enveloped by a large and partly transposed quartz chlorite alteration zone approximately 2 km in diameter and a distal but coherent pyrite quartz muscovite alteration zone extending as far as 4 km from the deposit chlorite talc in the mine area is notably magnesium rich and contains anomalous f ba zn and mn high fluorine is also present in coexisting muscovite and phlogopite the magnesium rich chlorite alteration contrasts sharply with the iron enrichment observed in many other felsic volcanic hosted precambrian massive sulfide deposits this may indicate fixation of iron by large amounts of pyrite in the section or entrainment of large amounts of seawater in the hydrothermal upflow zones kyanite is developed locally in the chlorite rich pipe at kristineberg in response to regional thermal metamorphism of highly aluminous alteration in the immediate foot wall rocks spectacular andalusite bearing quartz muscovite schists and quartz biotite cordierite schists also occur where the altered felsic volcanic rocks are intruded by the late revsund granite however similar metamorphic mineral growth is not observed where the volcanic rocks at the contact are less altered deposits near the top of the felsic volcanic succession are characterized by magnesium rich chlorite alteration in the foot wall and proximal calc silicate assemblages dolomite calcite tremolite garnet margarite where the host sedimentary rocks are carbonate rich in general the calc silicate alteration is restricted to the immediate hanging wall and zones lateral to the deposits and does not represent a regionally extensive exploration target the two main ore horizons in the kristineberg area are not linked by any obvious discordant structures or alteration zones however mineral chemical studies highlight several possible fluid flow pathways leading from the kristineberg deposit to the ravliden ore horizon more than 2 km upsection overprinting regional metamorphic minerals have inherited the hydrothermal signature of the ore related alteration electronic supplementary material is available at http dx doi org 10 1007 s00126 002 0299 y on that page frame on the left side a link takes you directly to the supplementary material

relationships between mineral composition and relative ages of iron nodules in jurassian soil sequences abstract iron nodules with several kinds of morphology occur in upland and lowland soil toposequences of the jura the upland soils contain spherical concretions m and tubular coatings both types being newly formed in the present pedoenvironments impregnative micritic concentrations in soil matrix and surrounding roots nodule fragments show concentric rings wherein goethite cements quartz grains and encloses feldspars and chamosite these minerals are characteristic of the eolian post wurmian dust and enable the upland nodules to be dated to post wurmian age the lowland soils contain polished and dense spherical concretions 500 m and twin nodules they are considered as inherited from a pre wurmian period of pedogenesis because they do not include eolian post wurmian minerals the spherical nodules are goethitic they are thought to be inherited from periglacial periods that induced hydromorphic environments such as those occurring currently in the uplands the twin nodules are hematitic they are thought to be relics of older weathering

pre 1 87 ga development of crustal domains overprinted by 1 87 ga transpression in the palaeoproterozoic skellefte district sweden the complex structural evolution within the vms hosting skellefte district sweden has been investigated to provide a solid structural framework for the known mineral deposits in the area the are

an investigation of the deforming layer debris rich basal ice continuum illustrated from three alaskan glaciers three small alaskan glaciers with different bed conditions were studied exit glacier had a thin deforming layer and produced subglacial and proglacial glaciotectonic land forms childs glacier also had a thin deforming layer but the upper part was frozen to the ice matanuska glacier had no deforming layer but had subglacial debris rich ice since it has been shown that sediment at the base can account for the majority of ice movement it is suggested that there is a deforming bed debris rich continuum whereby similar processes occur throughout the different subglacial environments these include similar longitudinal deformation patterns compression at the margin extension and simple shear up glacier similar vertical deformation patterns increase in deformation and fabric strength upwards through the sequence leading to the attenuation of stratified ice into dispersed ice and similar and interrelated incorporation processes the major differences were that the processes occurred at a much faster rate within the deforming layer and that probably only the deforming layer will be recorded in the geological record

paleopedology of terrae rossae rodoxeralfs from quaternary calcarenites in nw morocco abstract selected terrace rossae or rhodoxeralfs from calcarenites in all probability of mid pleistocene age in the vicinity of rabut show a strong mineral weathering and a considerable to extensive formation of clay minerals especially of kaolinites main sources of pedogenic kaolinites mostly of a disordered structure and poor cristallinity are primary feldpars 2 m and smectites 2 0 2 and

systematics of chlorite alteration at the phelps dodge massive sulfide deposit matagami quebec hydrothermal alteration at the phelps dodge archcan volcanogenic massive sulfide deposit has converted rhyodacite and rhyolite footwall rocks into the following mineral assemblages quartz chlorite albite epidote or sericite quartz chlorite or sericite chlorite or sericite and chlorite talc or stilpnomelane alteration at constant al was initiated by hydration addition of fe mg silicification and leaching of ca na which produced al saturated chlorites with a wide range of fe fe mg ratios within the assemblage quartz chlorite albite epidote or sericite with continued addition of fe and less mg combined with extensive leaching of quartz the chlorite became al undersaturated quartz chlorite talc assemblage and ultimately formed a rock composed essentially of chlorite the chlorite talc or stilpnomelane assemblage is stable in late crosscutting veinlets and in the ore zone chlorites in the si al mg fe system form a rectangular solid solution plane with limited substitution of al for si and extensive substitution of fe for mg in si al space the solid solution plane is outlined by al saturation presence of other al rich mineral and al undersaturation presence of al poor or al free mineral boundaries al iv substitution for si in the chlorites increases from 2 3 to 3 01 formula units based on 8 si al iv with fe fe mg whereas al iv occupancy decreases from 2 88 to 2 65 the valence charge balance is compensated by octahedral site vacancies or by the conversion of fe super 2 to fe super 3 the al iv content of chlorite also increases with temperature chlorites on the al saturated boundary of the solid solution field form a potentially useful geothermometer t degrees c 106 al iv 18 al iv is corrected for changes with the fe fe mg ratio as al iv corrected al iv 0 7 fe fe mg the fe fe mg ratios of bulk rock and contained chlorite correlate well birefringence colors of the chlorite change from green to brown violet and berlin blue as fe fe mg changes from 0 18 to 0 64 the fe fe mg variation apparently depends largely on the proportions of mg rich seawater and fe rich hydrothermal fluid in the altering brine

correlation between distribution and shape of vms deposits and regional deformation patterns skellefte district northern sweden the skellefte district in northern sweden is host to abundant volcanogenic massive sulphide vms deposits comprising pyritic massive semi massive and disseminated zn cu au pb ores surrounded by disseminated pyrite and with or without stockwork mineralisation the vms deposits are associated with palaeoproterozoic upper crustal extension d1 that resulted in the development of normal faults and related transfer faults the vms ores formed as sub seafloor replacement in both felsic volcaniclastic and sedimentary rocks and partly as exhalative deposits within the uppermost part of the volcanic stratigraphy subsequently the district was subjected to deformation d2 during crustal shortening comparing the distribution of vms deposits with the regional fault pattern reveals a close spatial relationship of vms deposits to the faults that formed during crustal extension d1 utilising the syn extensional faults as fluid conduits analysing the shape and orientation of vms ore bodies shows how their deformation pattern mimics those of the hosting structures and results from the overprinting d2 deformation furthermore regional structural transitions are imitated in the deformation patterns of the ore bodies plotting the aspect ratios of vms ore bodies and the comparison with undeformed equivalents in the hokuroko district japan allow an estimation of apparent strain and show correlation with the d2 deformation intensity of the certain structural domains a comparison of the size of vms deposits with their location shows that the smallest deposits are not related to known high strain zones and the largest deposits are associated with regional scale high strain zones the comparison of distribution and size with the pattern of high strain zones provides an important tool for regional scale mineral exploration in the skellefte district whereas the analysis of ore body shape and orientation can aid near mine exploration activities

satellite radar interferometry for monitoring ice sheet motion application to an antarctic ice stream satellite radar interferometry sri provides a sensitive means of monitoring the flow velocities and grounding line positions of ice streams which are indicators of response of the ice sheets to climatic change or internal instability the detection limit is about 1 5 millimeters for vertical motions and about 4 millimeters for horizontal motions in the radar beam direction the grounding line detected by tidal motions where the ice goes afloat can be mapped at a resolution of 0 5 kilometer the sri velocities and grounding line of the rutford ice stream antarctica agree fairly well with earlier ground based data the combined use of sri and other satellite methods is expected to provide data that will enhance the understanding of ice stream mechanics and help make possible the prediction of ice sheet behavior

satellite image derived velocity field of an antarctic ice stream the surface velocity of a rapidly moving ice stream has been determined to high accuracy and spatial density with the use of sequential satellite imagery variations of ice velocity are spatially related to surface undulations and transverse velocity variations of up to 30 percent occur such large variations negate the concept of plug flow and call into question earlier mass balance calculations for this and other ice streams where sparse velocity data were used the coregistration of images with the use of the topographic undulations of the ice stream and the measurement of feature displacement with cross correlation of image windows provide significant improvements in the use of satellite imagery for ice flow determination

clay composition and properties in termite mounds of the lubumbashi area d r congo article i nfo the influence of macrotermes falciger activity on clays sesquioxides and water dispersible clay wdc con tent was investigated by a physico chemical mineralogical and micromorphological study of termite mound and control soil profiles at various sites near lubumbashi se katanga d r congo x ray diffraction reveals that the termite mound materials are enriched in 2 1 clays especially mica and expandable clay min erals and selective dissolution analyses show that they contain greater relative amounts of mn oxides and poorly crystalline fe oxides relative to the surrounding ferralsols the water dispersible clay wdc content is much higher 4 87 fold in epigeal mound parts than in the control soils enrichment in 2 1 clays of the mounds is attributed to upward transport of mica and smectite as part of soil aggregates or saprolite mate rials used in mound construction the difference in nature and abundance of sesquioxides between termite mound and control soil is related to a difference in moisture regime whereby the basal part of the mounds are characterized by conditions with alternating reducing oxidizing conditions in contrast to the surround ing well drained ferralitic soils the much greater degree of clay dispersibility in termite mound materials than in the surrounding soils is mainly due to differences in clay properties primarily surface charge charac teristics and to differences in fe oxide content and mode of occurrence the high water dispersible clay con tent of termite mound materials is confirmed by micromorphological features including abundant clay coatings and fragments of coatings

the palaeoproterozoic kristineberg vms deposit skellefte district northern sweden part ii chemostratigraphy and alteration the kristineberg massive sulfide deposit is hosted by metamorphosed volcanic and subvolcanic rocks of the palaeoproterozoic skellefte group the deposit consists of 1 two main massive sulfide horizons the a ores and b ores which dip steeply southwards and are separated by 100 150 m and 2 the einarsson zone a complex interval of cu au rich stockwork sulfides and small massive sulfide lenses in altered and deformed rocks near the 1 000 m level the einarsson zone occurs some 20 100 m south of the b ores there are no definite younging indicators in the mine sequence in many areas of the mine the original host rocks are impossible to identify petrographically due to the abundance of secondary minerals such as quartz chlorite muscovite cordierite andalusite phlogopite pyrite and talc combined with variably schistose fabrics application of immobile element methods to 600 recent whole rock chemical analyses has however allowed the original rock types to be identified and correlated rhyolite x lies immediately north of the a ore while andesitic to dacitic to rhyodacitic rocks make up the 100 150 m interval between the a ore and b ore and massive rhyolite a lies immediately south of the b ore the felsic rocks are mostly of calc alkaline affinity excluding rhyolite x which is transitional the mine porphyry which lies north of the a ore and forms the marginal phase of the synvolcanic viterliden intrusive complex is compositionally similar to dacite and rhyodacite mass changes calculated for all rock types indicate that most of the volcanic rocks in the mine area are strongly depleted in na and ca and have gained variable amounts of mg and fe whereas si changes range from negative to positive gains in fe and changes in si are largest within 5 10 m of the massive sulfide lenses cordierite bearing schists of andesitic to felsic compositions that lie between massive sulfide lenses a and b are not as altered the einarsson zone commonly shows large gains in fe and mg while si shows large gains to large losses immobile element ratios indicate that very different secondary assemblages in the mine e g andalusite quartz muscovite and cordierite chlorite talc can be produced from the same precursor volcanic unit e g rhyolite conversely the same secondary mineral assemblage can be produced from different rocks e g weakly altered andesite and strongly altered rhyolite the common presence of cordierite andalusite in the mine area without anthophyllite is unusual in the alteration systems of volcanic hosted massive sulfide deposits and is proposed to have formed by the metamorphic reaction of the synvolcanic alteration minerals kaolinite and chlorite to produce cordierite where kaolinite was in excess of chlorite andalusite was also formed we propose that highly acidic alteration fluids locally produced high al minerals such as kaolinite that either overprinted or occurred in place of a more typical sericite chlorite quartz alteration assemblage that otherwise formed near the massive sulfide lenses application of lithogeochemical methods to the altered deformed and metamorphosed kristineberg rocks has identified specific volcanic contacts with massive sulfide potential and quantified the effects of synvolcanic hydrothermal alteration such an approach can increase the effectiveness of mineral exploration in metamorphosed terrains

formation of volcanogenic massive sulfide deposits the kuroko perspective abstract the main objective of this paper is to identify the geochemical hydrological igneous and tectonic processes that led to the variations in the physical size geometry and chemical mineralogy metal ratios and zoning characteristics of volcanogenic massive sulfide deposits with respect to space from a scale of mining district size area to a global scale and time from a all volcanogenic massive sulfide deposits vmsds appear to have formed in extensional tectonic settings such as at mid ocean spreading centers backarc spreading centers and intracontinental rifts and failed rifts all vmsds appear to have formed in submarine depressions by seawater that became ore forming fluids through interactions with the heated upper crustal rocks submarine depressions especially those created by submarine caldera formation and or by large scale tectonic activities e g rifting become most favorable sites for the formation of large vmsds because of hydrological physical and chemical reasons the fundamental processes leading to the formation of vmsds include the following six processes 1 1 intrusion of a heat source typically a 10 3 km size pluton into an oceanic crust or a submarine continental crust causes deep convective circulation of seawater around the pluton the radius of a circulation cell is typically 5 km the temperature of fluids that discharge on the seafloor increases with time from the ambient temperature to a typical maximum of 350 c and then decreases gradually to the ambient temperatures in a time scale of 100 to 10 000 years the majority of sulfide and sulfate mineralization occurs during the waxing stage of hydrothermal activity 2 2 reactions between low temperature t 2 4 as disseminated gypsum and anhydrite in the country rocks 3 3 reactions of the modified seawater with higher temperature rocks at depths during the waxing stage cause the transformation of the seawater to metal and h 2 s rich ore forming fluids the metals and sulfide sulfur are leached from the county rocks the previously formed gypsum and anhydrite are reduced by fe 2 bearing minerals and organic matter providing additional h 2 s the mass of high temperature rocks that provide the metals and reduced sulfur is typically 10 11 tons 40 km 3 in volume the roles of magmatic fluids or gases are minor in most massive sulfide systems except for so 2 to produce acid type alteration in some systems 4 4 reactions between the ore forming fluids and cooler rocks in the discharge zone cause alteration of rocks and precipitation of some ore minerals in the stockwork ores 5 5 mixing of the ore forming fluids with local seawater within unconsolidated sediments and or on the seafloor causes precipitation of primitive ores with the black ore mineralogy sphalerite galena pyrite barite anhydrite 6 6 reactions between the primitive ores with later and hotter hydrothermal fluids cause transformation of primitive ores to matured ores that are enriched in chalcopyrite and pyrite variations in the mineralogical and elemental characteristics the geometry and the size of submarine hydrothermal deposits are controlled by the following four parameters 1 a the chemical and physical characteristics of seawater composition temperature density which depend largely on the geographical settings e g equatorial evaporating basins 2 b the chemical and physical characteristics of the plumbing system lithology fractures 3 c the thermal structure of the plumbing system which is determined largely by the ambient geothermal gradient and the size and temperature of the intrusive and 4 d the physical characteristics of the seafloor depth basin topography for example the submarine hydrothermal deposits developed in basaltic plumbing systems are generally poor in pb and ba compared to those developed in felsic plumbing systems the lower temperature systems are generally poorer in sulfides but richer in iron oxides and sulfates the higher temperature and larger hydrothermal systems tend to produce chalcopyrite and pyrite rich ores contrasts in the metal ratios between the noranda type archean vmsds and the younger vmsds reflect the differences in the geothermal gradient of the plumbing systems the submarine hydrothermal deposits developed in the near equatorial regions tend to form large continuous bedded type ores because of the likeliness of creating large stratified basins the basic processes of submarine hydrothermal mineralization have remained essentially the same throughout the geologic history from at least 3 5 billion year ago to the present

velocity and strain rates derived from insar analysis over the amery ice shelf east antarctica we use displacements derived from matching complex synthetic aperture radar data using maximum coherence to generate a dense network of velocity estimates over the amery ice shelf from these velocities we generate the horizontal strain rate components and resolve them with respect to the local flow direction we present the spatial distributions of velocity and transverse shear strain rate and use them to investigate features of the flow regime for the shelf from the southern end of the shelf velocity decreases from a high of about 800ma 1 to around 300 ma 1 and then increases to a maximum of about 1350ma 1 at the centre of the front strain rates vary systematically across and along the shelf the pattern of the transverse shear strain rate clearly identifies the shear margins where values exceed 0 1 a 1 in the southern section of the shelf the pattern also shows longitudinal bands of enhanced shear strain rate containing ice with a strong preferred crystal fabric that was advected from shear margins upstream in the northern section of the shelf significant values of longitudinal and traverse stresses lead to enhanced shear deformation through their effect on the octahedral shear stress term

the determination of displacement fields from geodetic data along a strike slip fault observations of angles or distances between stations of a geodetic network are commonly used to infer information about the movement of the surface of the earth the absence of any observations external to the network leads to an ambiguous displacement field existing techniques for eliminating this ambiguity are all unsatisfactory in some respect the best technique an inner coordinate solution is not appropriate for networks located in a strike slip fault environment the inner coordinate solution zeros the rotation of all stations about their center of mass along a strike slip fault like the san andreas however motion normal to the fault is less likely than motion parallel to the fault the solution presented here an outer coordinate solution finds the rotation of the network that minimizes the components of displacement normal to the fault since motion along a strike slip fault is generally expected to be parallel to the fault the displacements obtained with the outer coordinate solution are more reasonable than those obtained with other techniques examination of a trilateration network near san francisco bay demonstrates the large effect that the choice of adjustment technique can have on the inferred relative motion of the two sides of the fault the inner coordinate solution gave a rate of about 1 mm yr whereas the preferred outer coordinate solution rate was 36 mm yr

a 1000 year climate ice core record from the guliya ice cap china its relationship to global climate variability in 1992 an american chinese expedition successfully recovered three ice cores 308 6 93 2 and 34 5m from the guliya ice cap summit 6710 m a s l in the far western kunlun on the qinghai tibetan plateau china guliya resembles a polar icecap with 10 m 200 m and basal temperatures of 15 6 5 9 and 2 1 c respectively the 308 6 m core to bedrock is the longest ice core retrieved from an elevation greater than 4000 m a s l and provides the first ice core history from the western side of the qinghai plateau the plateau experiences a pronounced annual precipitation cycle during which 70 80 of annual total precipitation falls in the summer monsoon season this leads to a marked visible stratigraphy in the glaciers which allows accurate dating of the ice cores and reconstruction of the net mass accumulation this paper presents 1 the results of the geophysical program to determine ice thickness ice flow and surface topography 2 an assessment of net accumulation from stake measurements snow pits and shallow core samples and 3 the analyses of the upper 100 m of the 308 6 m core which provide a 1000 year history including the little ice age which is compared with chinese historical records extended periods of positive accumulation on guliya are closely contemporaneous with dry periods in eastern china a trans pacific teleconnection is suggested by the strong temporal coherence between extended wet and dry phases on guliya and on the quelccaya ice cap peru

preservation of basal ice sediment texture in ice sheet moraines ice sheet moraines near kangerlussuaq in west greenland inherit distinctive particle size distributions from basal ice although debris structures from the basal ice are commonly destroyed by deposition and resedimentation processes the abundance of clay and silt in the dispersed faciesa basal ice at the ice sheet margin is clearly re ected in the sedimentology of the ice sheet moraine geographical variations in the texture or grain size of moraine sediments may thus re ect geographical variations in basal ice this o ers a new approach to reconstructing the basal ice characteristics and hence the thermal and dynamic properties of former ice sheets 2000 elsevier science ltd all rights reserved

pedogenesis permafrost substrate and topography plot and landscape scale interrelations of weathering processes on the central eastern tibetan plateau article i nfo weathering indices wi and pedogenic oxidesratios por were used to describe patterns of weathering inten sities and pedogenesis along climatic gradients mainly affected by varying influences of the asian and indian monsoon these climate settings induce particular soil moisture sm conditions in turn closely related to per mafrost state substrate and topography nine sites including a total of 30 soil profiles were examined along an eastern and a western transect across the central eastern qinghai tibet plateau additionally differences between four soil groups were analysed according to our knowledge the presented study is the first attempt of a comprehensive application of different wi and por to substrates of currently permafrost affected soils it providesanevaluation ofvarious tools intermsof chemicallydescribinganddifferentiating the relatedprocesses todistinctenvironmentalsettingsinlow weatheringregions wefoundthatweatheringtrendsalongtheclimat ic gradients could be clearly outlined by wi whereas por rather account for small scale variations describing significant differences of pedogenesis between continuous and discontinuous permafrost conditions pyrophos phate soluble iron fep proved to be useful for differentiating permafrost and ground water influenced soils showing a strong correlation to total organic carbon r 0 89 the chemical index of alteration cia is the

the spectrum of ore deposit types volcanic environments alteration halos and related exploration vectors in submarine volcanic successions some examples from australia variations in shape metal content alteration mineralogy and volcanic host rocks of the ore deposits in the two major volcanic hosted massive sulfide vhms districts of eastern australia the cambrian mount read volcanics and the cambro ordovician mount windsor subprovince strongly reflect their volcanic environment conditions of ore formation and hydrothermal alteration processes lens and sheet style polymetallic zinc rich deposits such as rosebery hellyer que river and thalanga are considered to have formed in moderate to relatively deep water environments 500 1 000 m these deposits probably formed either on the sea floor e g hellyer que river or by replacement of porous volcaniclastic units directly below the sea floor e g rosebery the footwall alteration associated with these polymetallic vhms deposits was controlled by host rock permeability and porosity which are in turn related to volcanic facies type degree of fracturing and synvolcanic structural architecture focusing of hydrothermal fluids along synvolcanic structures has resulted in well zoned chlorite sericite footwall alteration pipes within footwall lavas at hellyer on the other hand diffuse fluid flow through very thick pumice breccia at rosebery and hercules has resulted in strata bound sericite dominated footwall alteration zones parallel to the paleosea floor and the ore lenses massive and disseminated pyritic cu au deposits such as those in the mount lyell field and at highway reward formed by subsea floor replacement and are associated with only minor zinc lead massive sulfide ore these deposits formed from higher temperature fluids 300 degrees c in which copper transport is enhanced and are commonly located in felsic volcanic centers dominated by shallow porphyritic intrusions e g highway reward the cu au ore lenses may be strata bound e g mount lyell or crosscutting pipes e g highway reward depending on the structure and permeability characteristics of the felsic volcanic host rocks the presence of high sulfidation alteration minerals e g pyrophyllite zunyite in some of the cu au deposits e g mount lyell field indicates that fluids were relatively acidic and suggests the possibility of magmatic fluid input into the hydrothermal system alteration zonation associated with the cu au vhms deposits is more symmetrical than that of the zn rich deposits with sericite rich alteration extending into the hanging wall in keeping with the subsurface replacement origin of these deposits synvolcanic gold rich deposits with high gold base metal ratios are less common than the cu au and zn rich vhms ore types the gold rich ores e g henty south hercules are strata bound in nature have low sulfide contents and are associated with central zones of intense silicification surrounded by envelopes of sericite pyrite and carbonate alteration volcanological and geochemical studies at henty indicate the gold rich ore formed by the replacement of particular volcanic units deposited in a relatively shallow water environment dominated by volcaniclastic facies lavas and limestones this spectrum of cu au zn rich and au only deposits in the mount read volcanics and the mount windsor subprovince is interpreted to represent a continuum from classic sea floor vhms ores toward those with features more akin to porphyry cu au and epithermal au ag deposits this spectrum relates to the interplay between factors in the submarine volcanic environment and the character of the hydrothermal fluid as follows 1 proportions of volcaniclastic lava and subvolcanic intrusive facies 2 depth of seawater 3 permeability and porosity of volcanic host rocks 4 balance between magmatic components and seawater components in the ore fluid and 5 temperature and acidity of the ore fluid mineralogical lithogeochemical and isotopic studies have revealed a range of alteration vectors useful in exploration for both the zn rich and cu au vhms deposits carbonate and white mica compositional variations are highlighted as important mineralogical vectors thallium and antimony halos may be useful trace element vectors and oxygen and sulfur provide important isotope vectors toward the center of the hydrothermal system

occurrence and transformations of iron and manganese in a colluvial terra rossa toposequence of northern italy abstract a soil toposequence in ne italy was studied which consists of a terra rossa on cretaceous limestone on the upper slope grading downwards into a colluvial fan with terra rossa material and finally into alluvial river sediments it is postulated that the red colluviated terra rossa material has come under a moister hydroregime which provided reducing conditions because hematite of the terra rossa dissolved preferentially over goethite as shown by quantitative fe oxide mineralogy soil color changed from 2 5yr to 7 5yr the soils contained two types of concretions red ones with a low feo fed ratio and a high content of hematite and low content of mn oxides and black ones with a high feo fed ratio a small amount of hematite and abundant mn oxides the red concretions are therefore considered as inherited from an earlier period of pedogenesis whereas the black ones are neoformed in the present pedoenvironment this is further supported by the lower al for fe substitution of goethite in the black concretions as compared to a higher al substitution in the goethite inherited from the terra rossa

the little ice age as recorded in the stratigraphy of the tropical quelccaya ice cap the analyses of two ice cores from a southern tropical ice cap provide a record of climatic conditions over 1000 years for a region where other proxy records are nearly absent annual variations in visible dust layers oxygen isotopes microparticle concentrations conductivity and identification of the historical a d 1600 huaynaputina ash permit accurate dating and time scale verification the fact that the little ice age about a d 1500 to 1900 stands out as a significant climatic event in the oxygen isotope and electrical conductivity records confirms the worldwide character of this event

over estimation of efficiency of weathering in tropical red soils its importance for geoecological problems abstract weathering and soil formation rates are regarded as the main criteria of a tolerable soil loss the efficiency of weathering in the seasonal semiarid tropics has often been greatly over estimated especially in the geomorphologic literature in which weathering is assumed to be as fast or even faster than surface erosion six selected red soils in two intramontane basins of hyperthermic sw nepal near the border with india with 1500 1750 mm annual rainfall 5 humid months and a black soil near baroda gujarat india 3 4 humid months were studied mineralogically two of the red soils have tl ages between 10 and 30 ka the black soil has one of about 10 ka the yellowish silty parent material of the red soils is a preweathered soil sediment it contains only small amounts of easily weatherable primary minerals around 5 feldspars and 10 15 phyllosilicates dominantly muscovites surprisingly little pedogenic clay mineral formation could be identified the illites and kaolinites are predominantly of detrital origin the few non regular mixed layer minerals in the fine clay fraction

low melt rates with seasonal variability at the base of fimbul ice shelf east antarctica revealed by in situ interferometric radar measurements basal melt is a major cause of ice shelf thinning affecting the stability of the ice shelf and reducing its buttressing effect on the inland ice the fimbul ice shelf fis in dronning maud land dml east antarctica is fed by the fast flowing jutulstraumen glacier responsible for 10 of ice discharge from the dml sector of the ice sheet current estimates of the basal melt rates of the fis come from regional ocean models autosub measurements and satellite observations which vary considerably this discrepancy hampers evaluation of the stability of the jutulstraumen catchment here we present estimates of basal melt rates of the fis using ground based interferometric radar we find a low average basal melt rate on the order of 1 m yr with the highest rates located at the ice shelf front which extends beyond the continental shelf break furthermore our results provide evidence for a significant seasonal variability

iron oxide mineralogy of terra rossa and its genetic implications abstract fe d fe d fe t hematite geothite ratios and al substitution in hematite and goethite were found to vary to a rather limited extent in 48 terra rossa samples from various locations around the world this seems to indicate a rather specific pedoenvironment in which terra rossa is formed it is suggested that this pedoenvironment is characterized by an association of mediterranean climate high internal drainage due to the karstic nature of a hard limestone and neutral ph conditions under those conditions relatively high amounts of fe are released fe d fe t ca 0 7 from autochthonous and or allochthonous primary fe sources followed by preferential formation of hematite over goethite both having a medium level of al substitution the close association between terra rossa and the underlying limestone must therefore be seen in the role the rock plays for the water and air regimes of the soil rather than in its material characteristics except for soil ph neither an fe content in the limestone insufficient to explain the fe content of the solum nor the addition of eolian or alluvial material can therefore be used as an argument against a genetic relationship between terra rossa and its underlying limestone

reliability analysis for design of stake networks to measure glacier surface velocity measurement of glacier surface velocity provides some constraint on glacier flow models used to date ice cores recovered near the flow divide of remote high altitude ice caps the surface velocity is inferred from the change in position of a network of stakes estimated from the least squares adjustment of geodetic observations terrestrial and or spaced based collected approximately 1 year apart the lack of outliers in and the random distribution of the post fit observation residuals are regarded as evidence that the observations contain no blunders however if the network lacks sufficient geometric redundancy the estimated stake positions can shift to fit erroneous observations to determine the maximum size ofthese potential undetected shifts given the covariance of the observations and the approximate network geometry expressions are developed to analyze a network for redundancy number and marginally detectable blunders internal reliability and the position shifts from marginally detectable blunders external reliability two stake networks one on the col of huascaran 9 07 s 77 37 w 6050 m a s l in the north central andes of peru and one on the guliya ice cap 35 17 n 81 29 e 6200 m a s l on the qinghai tibetan plateau in china are examined for precision and internal and external reliability

syn extensional faulting controlling structural inversion insights from the palaeoproterozoic vargfors syncline skellefte mining district sweden the vargfors basin in the central skellefte district sweden is an inverted sedimentary sub basin within a palaeoproterozoic 1 89 ga marine volcanic arc the sub basin formed from upper crustal

derived bedrock elevations strain rates and stresses from measured surface elevations and velocities jakobshavns isbrae greenland jakobshavns isbrae 69 10 n 49 59 w drains about 6 5 of the greenland ice sheet and is the fastest ice stream known the jakobshavns isbrae basin of about 10 000 km 2 was mapped photogrammetrically from four sets of aerial photography two taken in july 1985 and two in july 1986 positions and elevations of several hundred natural features on the ice surface were determined for each epoch by photogrammetric block aerial triangulation and surface velocity vectors were computed from the positions the two flights in 1985 yielded the best results and provided most common points 716 for velocity determinations and are therefore used in the modeling studies the data from these irregularly spaced points were used to calculate ice elevations and velocity vectors at uniformly spaced grid points 3 km apart by interpolation the field of surface strain rates was then calculated from these gridded data and used to compute the field of surface deviatoric stresses using the flow law of ice for rectilinear coordinates x y pointing eastward and northward and curvilinear coordinates l t pointing longitudinally and transversely to the changing ice flow direction ice surface elevations and slopes were then used to calculate ice thicknesses and the fraction of the ice velocity due to basal sliding our calculated ice thicknesses are in fair agreement with an ice thickness map based on seismic sounding and supplied to us by k echelmeyer ice thicknesses were subtracted from measured ice surface elevations to map bed topography our calculation shows that basal sliding is significant only in the 10 15 km before jakobshavns isbrae becomes afloat in jakobshavns isfjord

tropical climate instability the last glacial cycle from a qinghai tibetan ice core an ice core record from the guliya ice cap on the qinghai tibetan plateau provides evidence of regional climatic conditions over the last glacial cycle 36 cl data suggest that the deepest 20 meters of the core may be more than 500 000 years old the 18 o change across termination i is 5 4 per mil similar to that in the huascaran peru and polar ice cores three guliya interstadials stages 3 5a and 5c are marked by increases in 18 o values similar to that of the holocene and eemian 124 000 years ago the similarity of this pattern to that of ch 4 records from polar ice cores indicates that global ch 4 levels and the tropical hydrological cycle are linked the late glacial stage record contains numerous 200 year oscillations in 18 o values and in dust nh 4 and no 3 levels

mineral deposits of canada a synthesis of major deposit types district metallogeny the evolution of geological provinces and exploration methods wayne d goodfellow editor 1 068 pp geological association of canada mineral deposits division special publication no 5 2007 hardcover isbn 13 978 1 897095 24 9 price members cdn 60 00 non members cdn 80 00 following in the footsteps of other landmark reviews of major ore producing countries such as australia hughes 1990 solomon and groves 1994 and south africa anhaeusser and maske 1986 this substantial 1 000 pages monograph is a great achievement that should be in every geologic research library in the world in many ways it sets a new standard most notably in that all figures and photographs are in color and that the entire volume is available in electronic form both as an included dvd and mostly on the gac website it is common in such compendia to have a spectacular cover photo or frontispiece to catch the reader s attention and this book does not disappoint the frontispiece photo is of a 61 8 kg sample from the dome mine timmins ontario and is stated to contain 20 wt percent gold at today s prices the gold alone would be worth 1 5 million dollars

3d modelling of hydrothermal alteration associated with vhms deposits in the kristineberg area skellefte district northern sweden this contribution presents a 3d assessment of metamorphosed and deformed hydrothermally altered volcanic rocks hosting the massive sulphide deposits of the kristineberg area in the 1 9 ga skellefte mining district in northern sweden using six calculated alteration parameters the ishikawa alteration index the chlorite carbonate pyrite index and calculated net mass changes in mgo sio2 na2o and ba the results which are also available as film clips in the supplementary data confirm inferences from geological mapping namely that the sericite and chlorite rich alteration zones have complex and cross cutting geometries and that most of these zones are semi regional in extent and range continuously from surface to over a kilometre deep the major known massive sulphide deposits occur proximal to zones characterised by coincidence of high values for the alteration index and chlorite carbonate pyrite index and large mgo gains which corresponds to zones rich in magnesian silicates these zones are interpreted as the original chlorite rich proximal parts the alteration systems and form anomalies extending up to 400 m away from the sulphide lenses in addition the stratigraphically highest vhms are hosted by rocks rich in tremolite talc chlorite and dolomite with lesser clinozoisite which have high chlorite carbonate pyrite index and low medium alteration index values reflecting a greater importance of some chlorite carbonate alteration at this stratigraphic level vectoring towards massive sulphide deposits in this area can be improved by combining the ai and ccpi indexes with calculated mass changes for key mobile elements of the ones modelled in this study mgo and sio2 appear to be the most useful

soil chronosequence development in dunes on the southeast african coastal plain maputaland south africa abstract dunes have accreted on the southeast african coastal plain in coast parallel patterns of degraded whaleback ridges sand megaridges and extended parabolic dunes since the pliocene in the maputaland dune field relative dating is complicated by soil degradation erosion and vegetation cover this project assessed alternative relative and numeric dating techniques that can be used to differentiate dune systems and eolian sand bodies soil profile characteristics were used to calculate soil development indices sdi for soil horizons sampled from hand augered holes and rare exposures infrared stimulated luminescence irsl dating of representative dunes and sand units helped define the pedogenesis achieved since deposition the quartzose dune sands have weathered to form very deep soil profiles enhanced sdi values for horizons or sampled intervals down the profile reflect ph decrease advanced rubification or distinct mottling clay increase and harder consistency with depth the youngest holocene profiles exhibit decreasing horizon index values with depth below the a horizon whereas late pleistocene profiles display sdi values increasing with depth within the upper 3 m of the profile within some mid to late pleistocene eolian sands greater profile horizonation and catena complexity manifests as complex soil profiles or distinctly mottled clay enriched horizons at depths of 2 5 m below the surface the sdi profiles from specific dune systems or stratigraphic units cluster well and effectively characterize soil development in dune sand units of different ages depositional age plotted against sampled horizon index values makes it possible to determine generalized rates of soil profile development and to compare pedogenic processes on the high rainfall coastal barrier dunes to those found in the drier interior sampled horizon index values distinguish buried soil profiles and highlight possible localized surficial reworking

mineralogical and geochemical characteristics of quaternary sediments from the island of susak northern adriatic croatia middle and upper pleistocene loess palaeosol sequences up to 90 m thick are exposed on the island of susak located in the northern adriatic sea in croatia during glacial times the sea level was up to about 120 m lower and a significant part of the adriatic became land the source area of the primary aeolian sediments was in the vicinity of the island and is related to the southward extended river po plain the loess has a mainly clayey to sandy silt or sand grain size and is intercalated by at least three tephras numerous palaeosols and calcareous segregations the heavy mineral association points to metamorphic and igneous rocks from alpine regions as source material of the loess geochemical and mineralogical properties of loess and palaeosols differentiate one from another and reflect the intensity of weathering and pedogenesis the oldest tephra contains vitroclasts and serrated clinopyroxene while the middle and the youngest tephra along with vitroclasts contain idiomorphic augite as diagnostic volcanic features based on bulk rock and vitroclast chemistry morphology of pyroxenes and the age of the loess sandwiching the tephra the potential source of this volcanic material could very likely be the campanian or aeolian volcanic province in southern italy infrared stimulated luminescence dating results show that the major part of the aeolian deposits including the tephra layers correlates to mis 3 mis 5

iron oxides and particle aggregation in b horizons of some italian soils the relative importance of iron oxides to the aggregation status of soil has been evaluated for thirteen samples collected from b horizons of inceptisols and alfisols the particle size distributions before and after selective dissolution treatments were performed to assess the capacity of various iron oxides to aggregate soil particles iron extractable with nh4 oxalate was more effective in aggregation than goethite and hematite the capacity of iron oxides to aggregate clay sized particles was not significantly different in samples containing goethite and hematite from those having goethite only goethite and hematite in clay and in sand fractions had similar al substitution and mean crystallite dimensions but different reductive dissolution rates in dithionite

the basal ice layer of glaciers and ice sheets abstract in many glaciers and ice sheets there is a basal ice layer bil in which the ice is conditioned primarily by processes operating at the bed the bil is chemically and physically distinctive and is characterised by a component of basally derived sediment the bil is a rheological control on ice sheet dynamics an indicator of subglacial conditions and processes an agent of subglacial geologic processes the source of a substantial proportion of glacial sediments a limit to the downward extension of the climate record from deep ice cores if debris characteristics of the bil are preserved in glacial sediments former glacier conditions can be inferred analysis of stable isotopes gas and cation composition ice crystallography debris composition and structural glaciology has elucidated many mechanisms for bil formation common elements can be identified from a range of locations key issues are entrainment of ice and debris from the bed formation of new ice metamorphism of existing ice in the bil and thickening of the bil by deformation a distinction can be made between basal ice formed by accretion of material from the bed stratified facies and basal ice formed by metamorphic processes within the ice close to the bed dispersed facies

optimal measurement of ice sheet deformation from surface marker arrays surface strain rate is best observed by fitting a strain rate ellipsoid to the measured movement of a stake network or other collection of surface features using a least squares procedure error of the resulting fit varies as 1 l delta t square root of n where l is the stake separation delta is the time period between initial and final stake survey and n is the number of stakes in the network this relation suggests that if n is sufficiently high the traditional practice of revisiting stake network sites on successive field seasons may be replaced by a less costly single year operation a demonstration using ross ice shelf data shows that reasonably accurate measurements are obtained from 12 stakes after only 4 days of deformation it is possible for the least squares procedure to aid airborne photogrammetric surveys because reducing the time interval between survey and re survey permits better surface feature recognition

yellowing bleaching and ferritisation processes in soil mantle of the western ghaˆts south india abstract a sequence of red through yellow to grey soils from well drained hilltops to poorly drained valleys is common on the backslopes of the western gha ts southern india detailed field observations along a representative toposequence developed from weathered schists and local petrographic mineralogical and chemical investigations are used to i link yellow white and brown features to yellowing bleaching and ferritisation processes and ii relate the enlargement of these features and the development of these processes to aquic and drainage conditions precise demarcation of soil morphological features at toposequence scale permits to differentiate an upslope ferralitic domain from a dowslope hydromorphic domain in each of these domains geometrical relationships expressed in terms of either concordance or discordance between horizon and colour boundaries are taken as arguments to point out that aquic conditions have expanded upslope in the landscape at some time in the past as a consequence partial and selective dissolution of iron oxides resulted in yellowing of reddish soil material dissolution which affected first hematite then gcethite was controlled by al substitution in the crystal structure of iron oxides it has been reproduced in the laboratory using a chemical reducing agent yellowing is associated with the onset of aquic conditions yellow colours occur predominantly at the periphery of the hydromorphic domain in the hydromorphic domain complete removal of iron oxides similarly resulted in bleaching of yellow materials and was linked to waterlogging iron mobilized by yellowing and bleaching processes moved along established flow paths and locally crystallized and concentrated in saprolite by ferritisation bleaching and ferritisation occurred downslope and downward into the soil to form the inner white brown zone of the hydromorphic domain the amount of iron stored in low lying positions and the development of weakly weathering conditions suggest that the internal drainage of the ground watertables was limited this study cannot conclude if yellowing bleaching and ferritisation are still actively occurring as no hydo geochemical investigations were conducted along the toposequence

rubefaction post wurmienne en climat montagnard humide jurassien role du pedoclimat et actualite du processus abstract post wurmian soils from a proglacial region nozeroy jura have been studied they have two b horizons which have developed under the same general climatic conditions a reddish horizon overlying a yellowish horizon analysis of the mineral phases leads to the conclusions that 1 the soils have the same aeolian wurmian origin from a nearby source 2 the recent pedogenetic development has involved the formation of hematite essentially from in situ modification of geothite hematite was identified in the argillaceous granulometric fraction by three methods colour x ray diffraction and mossbauer spectroscopy this pedogenetic change of geothite into hematite which may be quite recent is apparently favoured by the extremely fissured nature of the underlying rock and the stony nature of the soil the siting and organization of the soil rock interface lead to repeated cycles of wetting and drying and thus a pedoclimate with periods of desiccation sufficient to induce the formation of hematite the severe limitations associated with the mountain climate precipitation 1700 mm average temperature 6 c are in this case apparently less important than the interactions of climate and rocks the excellent drainage due to the highly fissured rocks results apparently in a pedological environment favourable to rubification in the horizons most subject to cycles of wetting and drying

holocene late pleistocene climatic ice core records from qinghai tibetan plateau three ice cores to bedrock from the dunde ice cap on the north central qinghai tibetan plateau of china provide a detailed record of holocene and wisconsin wurm late glacial stage lgs climate changes in the subtropics the records reveal that lgs conditions were apparently colder wetter and dustier than holocene conditions the lgs part of the cores is characterized by more negative 18 o ratios increased dust content decreased soluble aerosol concentrations and reduced ice crystal sizes than the holocene part these changes occurred rapidly 10 000 years ago in addition the last 60 years were apparently one of the warmest periods in the entire record equalling levels of the holocene maximum between 6000 and 8000 years ago

hydrothermal alteration associated with mesozoic granite hosted gold mineralization at the sanshandao deposit jiaodong gold province china abstract the sanshandao gold deposit reserves of more than 200 t au and average grade of 3 96 g t located at northwestern edge of the jiaodong peninsula eastern north china craton is one of the largest gold deposits in the jiaodong gold province in this deposit disseminated and stockwork style ores are hosted in mesozoic granitoids mineralization and alteration are largely controlled by the regional sanshandao cangshang fault host granitic rocks for the deposit display a complex paragenetic sequence of alteration and mineralization activities of the sanshandao cangshang fault created structurally controlled permeability allowing for infiltration of hydrothermal fluids leading to diffusive k feldspar alteration on the two fault planes later large scale diffusive sericitization symmetrically developed across the main fault and partially overprinted the earlier k feldspar alteration following the sericitization relatively small scale silicification occurred but now it is only retained in the hanging wall of the main fault subsequently the fault gouge formed as a barrier layer which is impermeable for later fluids to move upward after that strong pyrite sericite quartz alteration occurred only in the footwall of the main fault and was accompanied by gold precipitation the last stage carbonation and quartz carbonate veins marked the waning of gold related hydrothermal activity mass balance calculations indicate complex behaviors of different types of elements during fluid rock interaction most major elements were affected by intensive mineral replacement reactions as expected the fluid mobile elements lile and lree generally show moderate to high mobility it is notable that even the commonly assumed fluid immobile elements such as hree and hfse tend to be changed to various degrees in addition y ho zr hf and nb ta fractionations are observed in altered domains studies on alteration assemblages and fluid inclusions suggest that the ore forming fluids were characterized by low salinity 8 4 wt nacl equiv moderate temperature 300 400 c weakly acidic ph 3 5 and relatively reducing log fo2 28 characteristics in this type of fluids gold was most likely transported as au hs 2 complex with alteration going on log ak ah of fluids generally decreased due to significant formation of secondary k bearing minerals in addition there might be a decrease of fo2 from pre gold alteration stage to the main gold mineralization stage and decrease of fo2 was probably one of the factors controlling gold precipitation the sr and nd isotopic compositions of hydrothermal minerals combined with previous h o and he ar isotopic studies indicate that the hydrothermal fluids were mainly derived from crustal sources e g degassing of felsic magmas and meteoric water but with involvement of mantle derived components the gold mineralization event just coincided with reactivation of the north china craton as marked by asthenosphere upwelling voluminous igneous rocks and high crustal heat flow which may have provided sufficient heat energy and fluid input required for the formation of the gold deposits

interferometric radar observations of glaciar san rafael chile interferometric radar observations of glaciar san rafael chile were collected in october 1994 by nasa s spaceborne imaging radar c sir c at both l 24 cm and c band frequency 5 6 cm with vertical transmit and receive polarization the c band data did not yield good geophysical products because the temporal coherence of the signal was significantly reduced after 24 h the l band data were however successfully employed to map the surface topography of the icefield with a 10 m uncertainty in height and measure ice velocity with a precision of 4 mm d 1 or 1 4 ma 1 the corresponding error in strain rates is 0 05 a 1 at a 30 m horizontal spacing the one dimensional interferometric velocities were subsequently converted to horizontal displacements by assuming a flow direction and complemented by feature tracking results near the calving front the results provide a comprehensive view of the ice flow dynamics of glaciar san rafael the glacier has a core of rapid flow 4 5 km in width and 3 5 in average slope surrounded by slowermoving ice not by rock ice velocity is 2 6 m d 1 or 0 95 km a 1 near the equilibrium line altitude 1200 m increasing rapidly before the glacier enters the narrower terminal valley to reach 17 5 m d 1 or 6 4 km a 1 at the calving front strain rates are dominated by lateral shearing at the glacier margins 0 4 0 7 a 1 except for the terminal valley section where longitudinal strain rates average close to 1 a 1 this spectacular longitudinal increase in ice velocity in the last few kilometers may be a fundamental feature of tidewater glaciers

setting of zn cu au ag massive sulfide deposits in the evolution and facies architecture of a 1 9 ga marine volcanic arc skellefte district sweden the skellefte mining district occurs in an early proterozoic mainly 1 90 1 87 ga svecofennian magmatic province of low to medium metamorphic grade in the baltic shield in northern sweden the district contains over 85 pyritic zn cu au ag massive sulfide deposits and a few vein au deposits and subeconomic porphyry cu au mo deposits the massive sulfide deposits mainly occur within and especially along the top of a regional felsic dominant volcanic unit attributed to a stage of intense extensional continental margin arc volcanism from facies analysis we interpret the paleogeography of this stage to have comprised many scattered islands and shallow water areas surrounded by deeper seas all the major massive sulfide ores occur in below wave base facies associations however some ores occur close to stratigraphic intervals of above wave base facies associations and the summits of some volcanoes that host massive sulfides emerged above sea level intense marine volcanism was superceded at different times in different parts of the district by a stage of reduced volcanism uplift resulting in subregional disconformities and then differential uplift and subsidence resulting in a complex horst and graben paleogeography uplift of the arc is attributed to the relaxation of crustal extension and the emplacement of granitoids to shallow crustal levels a few massive sulfide ores formed within the basal strata of this second stage the horst and graben system was filled by prograding fluvial deltaic sediments and mainly mafic lavas and during this stage the skellefte district was a transitional area between renewed arc volcanism of more continental character to the north and subsidence and basinal mudstone turbidite sedimentation to the south this whole volcanotectonic cycle occurred within 10 to 15 m y we define 26 main volcanic sedimentary and intrusive facies in the skellefte district the most abundant facies are 1 normal graded pumiceous breccias which are interpreted as syneruptive subaqueous mass flow units of pyroclastic debris 2 porphyritic intrusions and 3 mudstone and sandstone turbidites facies associations define seven main volcano types which range from basaltic shields to andesite cones and rhyolite calderas despite this diversity of volcano types most massive sulfide ores are associated with one volcano type subaqueous rhyolite cryptodome tuff volcanoes these rhyolite volcanoes are 2 to 10 km in diameter 250 to 1 200 m thick at the center and are characterized by a small to moderate volume rhyolitic pyroclastic unit intruded by rhyolite cryptodomes sills and dikes massive sulfide ores occur near the top of the proximal near vent facies association the remarkable coincidence in space and time between the ores and this volcano type indicates an intimate genetic relationship between the ores and the magmatic evolution of the volcanoes many of the massive sulfide ores occur within rapidly emplaced volcaniclastic facies and are interpreted to have formed by infiltration and replacement of these facies some of the ore deposits have characteristics of both marine massive sulfides and subaerial epithermal deposits we suggest that massive sulfides in the skellefte district span a range in ore deposit style from deep water sea floor ores to subsea floor replacements to shallow water and possibly subaerial synvolcanic replacements facies models are provided for the mineralized rhyolite volcanoes and volcanological guides are provided for exploration for blind ores within these volcanoes

the palaeoproterozoic kristineberg vms deposit skellefte district northern sweden part i geology the kristineberg volcanic hosted massive sulphide vms deposit located in the westernmost part of the palaeoproterozoic skellefte district northern sweden has yielded 22 4 mt of ore grading 1 0 cu 3 64 zn 0 24 pb 1 24 g t au 36 g t ag and 25 9 s since the mine opened in 1941 and is the largest past and present vms mine in the district the deposit is hosted in a thick pile of felsic to intermediate and minor mafic metavolcanic rocks of the skellefte group which forms the lowest stratigraphic unit in the district and hosts more than 85 known massive sulphide deposits the kristineberg deposit is situated lower in the skellefte group than most other deposits it comprises three main ore zones 1 massive sulphide lenses of the a ore historically the main ore having a strike length of about 1 400 m and extending from surface to about 1 200 m depth 2 massive sulphide lenses of the b ore situated 100 150 m structurally above the a ore and extending from surface to about 1 000 m depth 3 the recently discovered einarsson zone which occurs in the vicinity of the b ore at about 1 000 m depth and consists mainly of au cu rich veins and heavily disseminated sulphides together with massive sulphide lenses on a regional scale the kristineberg deposit is flanked by two major felsic rock units massive rhyolite a to the south and the mine porphyry to the north the three main ore zones lie within a schistose deformed and metamorphosed package of hydrothermally altered dominantly felsic volcanic rocks which contain varying proportions of quartz muscovite chlorite phlogopite pyrite cordierite and andalusite the strongest alteration occurs within 5 10 m of the ore lenses stratigraphic younging within the mine area is uncertain as primary bedding and volcanic textures are absent due to strong alteration and tectonic folding and shearing in the vicinity of the ore lenses hydrothermal alteration has produced both mg rich assemblages mg chlorite cordierite phlogopite and locally talc and quartz muscovite andalusite assemblages both types of assemblages commonly contain disseminated pyrite the sequence of volcanic and ore forming events at kristineberg is poorly constrained as the ages of the massive rhyolite and mine porphyry are unknown and younging indicators are absent apart from local metal zoning in the a ores regional structural trends however suggest that the sequence youngs to the south the a and b ores are interpreted to have formed as synvolcanic sulphide sheets that were originally separated by some 100 150 m of volcanic rocks the einarsson zone which is developed close to the 1 000 m level is interpreted to have resulted in part from folding and dislocation of the b ore sulphide sheet and in part from remobilisation of sulphides into small zn rich massive sulphide lenses and late au cu rich veins however the abundance of strongly altered andalusite bearing rocks in the einarsson zone coupled with the occurrence of au cu rich disseminated sulphides in these rocks suggests that some of the mineralisation was synvolcanic and formed from strongly acidic hydrothermal fluids

ice deformation in the vicinity of the ice core site at taylor dome antarctica and a derived accumulation rate history knowledge of ice flow and strain rate in the vicinity of the taylor dome east antarctica ice core site enhances interpretation of the paleoclimate information from the ice core we measured surface ice motion by repeated optical and gps surveys of a network of 253 markers we developed a robust data reduction method that uses least squares based on singular value decomposition to simultaneously calculate positions and velocities of these markers in a geocentric coordinate system constrained by these surface velocities we used a finite element model to compute the modern ice velocity field at depth as the geometry of taylor dome appears to have been steady through the holocene we used particle paths from a steady state model to track ice particles to the ice core from their points of origin on the surface by removing the effects of path dependent vertical strain we derived past accumulation rates at the origin points of those particle paths from measured layer thicknesses in the ice core comparison with accumulation rates estimated from concentrations of 10 be and so 4 in the core suggests that significant amounts of snow were lost by wind scouring during the last glacial maximum and at 50 kyr bp