mechanical interactions between rigid particles in a deforming ductile matrix analogue experiments in simple shear flow abstract the mechanical interaction between two or more particles is investigated in newtonian simple shear flow the experimental models allow observation of both the particle rotation and the deformation pattern around the particles the finite and instantaneous strain patterns around rigid particles are strongly heterogeneous and asymmetric with high finite strain zones aligned to the direction of maximum finite stretch these correspond to local flow with low vorticity number heterogeneous strain patterns around rigid particles spread over a distance of 1 2 times the particle length and this distance increases with increasing bulk strain where rigid particles are more concentrated these patterns coalesce and the overall pattern is then strongly controlled by the particles and cannot be simply related to the external boundary conditions in rocks the characteristic asymmetric strain pattern around rigid isolated particles is a reliable shear criterion which becomes unreliable with high concentrations of rigid particles particle rotation is significantly disturbed when the distance between adjacent particles of equal size is shorter than their length that is only in very concentrated suspensions of rigid particles in a composite shape fabric the development of the sub fabric corresponding to the smaller minerals will be more disturbed

formation and persistence of mollisols on zeolitic deccan basalt of humid tropical india in contrast to generally observed non acidic and less weathered mollisols in temperate semi arid and humid climate acidic and fairly weathered mollisols on deccan basalt are observed in hills of central satpura range madhya pradesh and western india western ghats maharashtra under forest in the present tropical humid climatic conditions the detailed morphological chemical and mineralogical investigations of these mollisols of central and western india indicates that due to the presence of zeolites in the deccan basalt the transformation of smectite to kaolinite was prevented and the retention of adequate amount of smectite and continuous supply of calcium ions from zeolites made the formation of mollisols in forest even under tropical humid climate the formation and the persistence of these mollisols in association with acidic alfisols under sparse forest in the basaltic landscape of millions of years in central and western india demonstrates the primary importance of the quality of parent material rich in expanding clay mineral and bases in their formation this unique example thus expands the basic knowledge on the formation of mollisols in the humid tropical part of the world

soil genesis and mineralogy across a volcanic lithosequence abstract lithology is a principle state factor of soil formation interacting with climate organisms topography and time to define pedogenesis a lithosequence of extrusive igneous lithologies rhyolite obsidian dacite andesite and basalt was identified in the clear lake volcanic field in the coast range of northern california to determine the effects of lithology on pedogenesis clay mineralogy and soil physiochemical properties based on regional landscape erosion rates 0 2 0 5 mm yr 1 the soil residence times for the investigated pedons 150 cm deep were of the order of 3000 to 7500 years indicating that the soils developed under the relatively stable holocene mesic xeric climate regime soils from all lithologies developed to a similar xeralf taxonomy with remarkably consistent physiochemical properties although total fet and dithionite citrate extractable fed iron concentrations diverged across lithologies the degree of weathering as assessed by the fed fet ratio was similar across the lithosequence in spite of large differences in silica content of the parent materials the clay mineralogical assemblage of all lithologies was dominated by kaolin minerals kaolinite and or halloysite all pedons displayed an increase in halloysite and the degree of halloysite hydration with increasing depth except the basalt pedon which was dominated by kaolinite with only trace halloysite we attribute this lack of halloysite in the basalt pedon to the lower silica activities associated with this silica poor lithology there was a lack of nanocrystalline minerals across all lithologies as inferred from selective dissolution the dominance of crystalline materials is a function of the xeric soil moisture regime whereby summer soil profile desiccation promotes dehydration and crystallization of metastable nanocrystalline precursors further the pronounced summer dry period results in dehydration of halloysite 1 0 nm to halloysite 0 7 nm also referred to as meta halloysite in some literature together with transformation to kaolinite in the upper soil profile in spite of the relatively young soil residence times of these soils holocene age the effects of lithology persisted only in differences in fe oxide concentrations fed as well as a lack of significant halloysite in basalt pedons the overwhelming effect of climate in these highly weatherable parent materials narrowed the trajectory of pedogenesis resulting in soils from contrasting lithologies converging on kaolin mineralogy a lack of nanocrystalline constituents and similar soil physiochemical properties

chemistry and microstructures of clay particles in smectite rich shelf sediments south shetland islands antarctica the clay mineralogy of a holocene sediment core from the shelf of livingston island south shetland islands antarctica has been investigated by x ray diffraction xrd lattice imaging bulk chemical analysis of fine clay fractions and analytical transmission electron microscopy atem the clay minerals identified by xrd of 2 m fraction are smectite 63 chlorite 25 and illite 12 with little downcore variation lattice imaging of clay particles has confirmed the presence of interstratified illite smectite and interstratified chlorite smectite atem of ca saturated samples showed that the smectitic clay particles are rich in k fe and mg k in the smectitic particles is mostly present as a fixed cation in the interlayer confirming the presence of interstratified illite a comparison of the mineralogy of the bedrock soils in the probable source area and the core sediment strongly supports the view that the clay minerals must have originated by glacial erosion physical weathering and reworking of hydrothermally altered volcanic bedrock and tephra of the south shetland islands

palaeoclimatic interpretation of clay minerals in marine deposits an outlook from the continental origin abstract as distribution of clay minerals in modern oceans seems to be controlled by contemporary climates marine clays in ancient deposits have been widely used to reconstruct palaeoclimates in this review we examine this question mainly from the continental origin of the clay minerals and show the difficulties of retrospective analysis of the influence of climate on common marine deposits we examine successively how soils develop and behave are reworked and palaeoweatherings are preserved focusing the review on kaolinitic soils indicative of tropical wet climates several stages intervene between the time of clay mineral development in soils and their final deposition in the basin 1 the persistence over geological times of huge amounts of kaolinitic palaeoweathering materials in the landscapes may seriously alter the palaeoclimatic signal of kaolinite in the sedimentary record although the kaolinite deposited in recent sediments of the world oceans is consistent with wet climatic zones this is mainly because the major kaolinitic and bauxitic palaeosurfaces coincide with the tropical areas where kaolinite is still developing at present 2 possible development of deep kaolinitic profiles at high latitudes and cold conditions under co 2 enriched palaeoatmospheres or even by unusual acidic weathering linked with dry climates is misleading palaeoenvironments for palaeoclimatic reconstruction 3 erosion and transport processes always cloud the signal to some extent because frequently erosion products from the bedrock and different soil horizons will be mixed and major drainage systems may include soils of different climatic zones 4 the arrival of the soil clay assemblages in the basin inevitably lags against their formation on the continent and may occur several million years after formation of the soils on the continent and climate may have considerably changed at that time it is pointed out that sedimentologists and palaeoclimatologists should consider the complexity of the relations between soil and sedimentary clay minerals soil formation rates are slow and therefore the resolution of the palaeoclimatic record in marine clay may not be closer than 1 or 2 ma at present the palaeoclimatic interpretations of marine clay assemblages are yielding at best nothing more than rather broad palaeoclimatic information this approach cannot achieve the same degree of resolution as other techniques such as isotope or microfossil studies clay mineral assemblages may provide integrated records of overall climatic impacts whereas other techniques are more likely to reveal local or temporary climates

investigation of the clay minerals composition of soils derived from basalt parent materials in the early miocene to early pleistocene on the arabian shield using multiple techniques implications for paleoclimatic conditions knowledge of clay minerals composition can be used to understand paleoenvironmental and or paleoclimatic conditions particularly for soils derived from volcanic parent materials that were subjected to diverse climatic conditions during pedogenesis in this study the clay minerals composition in soils developed from basaltic parent materials during the cenozoic mostly during the early miocene to early pleistocene in the harrats region of the arabian shield in saudi arabia were investigated forty seven clay samples were examined using selective dissolution analyses x ray diffraction xrd thermogravimetric analysis tg fourier transform infrared spectroscopy atr ft ir scanning electron microscopy sem and transmission electron microscopy tem to obtain a better understanding of the clay minerals developed in basaltic parent materials particularly under a dry hot environment the xrd results revealed that the clay mineralogy was dominated by smectite kaolin kaolinite halloysite and interstratified vermiculite chlorite vm ch with mica pseudo chlorite palygorskite and ca zeolites as minor components the tem provided strong evidence for the presence of allophane and imogolite which is in line with numerous previous studies on soils formed from basaltic parent materials the existence of poorly crystalline minerals in these soils was strongly supported by the selective dissolution analysis results the combined influence of paleoclimates and parent material is evidenced in the clay minerals in the studied soils the formation of smectite vm ch and chlorite minerals in the harrats soils could be attributed to the simultaneous effect of temperate paleoclimates that dominated the pliocene and the wet transition periods that occurred through the pleistocene into the mid holocene while the minor palygorskite and ca zeolites could be related to the dry conditions that started in the late holocene and persist to the present day additional studies regarding the clay mineral assemblages in similar geoenvironmental settings are highly recommend and should account for paleoclimatic conditions to provide a better understanding of the relationship between clay minerals and paleoclimates

evidence for multiple ground rupturing earthquakes in the past 4 000 years along the pasuruan fault east java indonesia documentation of active normal faulting in the javan backarc

andisols of turkey an example from the cappadocian volcanic province abstract a number of studies have been conducted on the genesis of soils from volcanic deposits in semi humid and humid climates however there has been little study of the mineralogical properties and genesis of soils from volcanic rocks in arid and semi arid climates this study was conducted to understand the genesis of soils from different volcanic parent materials such as andesite dacite volcanic ash basalt and ignimbrite in the region east of the erciyes stratovolcano in central anatolia at least three soil profiles were selected from each parent material and 17 soil profiles were described soil samples were also taken from each soil horizon for physical chemical and mineralogical analyses soil profiles vary according to elevation and the types of derived parent materials and are divided into 17 pedons and 15 horizons 2a 2bw 2bw1 2c a2 bc bw bw1 bw2 bw3 c c1 c2 cr r soil acidity varied from slightly alkaline to slightly acidic in all soils organic matter contents were higher in the surface horizons and generally decreased with depth in all pedons the extractable cation values of ammonium oxalate pyrophosphate dithionite citrate and sodium pyrophosphate as well as unhydrolyzed volcanic glass allophone imogolite smectite and ferrihydrite contents of the soils are variable based on the parent materials pedons and elevations that are typical of the cappadocian volcanogenic soils in anatolia of turkey these soils can generally be described as alu andic andisols due to their alo 1 2feo values and alp alo ratios the important factors affecting the formation and development of soils are climatic variations affecting horizon development and genesis soil parent material diversities and leaching regimes originating from elevation differences

semi arid soils from a topolithosequence at james ross island weddell sea region antarctica chemistry mineralogy genesis and classification abstract climate and parent material have a significant impact on the development of antarctic soils and areas dominated by basaltic andesitic volcanic rocks sedimentary rocks and metamorphic rocks have been widely studied james ross island located in the semi arid transition between east antarctic peninsula weddell sea sector receives both continental and maritime climatic influences resulting in distinct transitional soil formation process in antarctica there is little research on semi arid soils formed on volcano sedimentary rocks as well as their pedogenetic processes in this study a topolithosequence of volcanic and sedimentary rocks in this semi arid transitional climate was investigated nine profiles three on marine terraces four on sedimentary rocks and two on volcanic rocks were described sampled and analyzed for morphological physical chemical and mineralogical properties soils are predominantly gelisols cryosols and present cryoturbation features despite the current dry climate vegetation is scarce and nesting birds are absent so that most soils can be characterized as ahumic all profiles have a skeletic character with a high percentage of coarse materials the soil ph varied from neutral to alkaline and the potential acidity values were null the mineralogy of the clay fraction presented kaolinite which was likely inherited from warmer and wetter paleoclimatic conditions during sedimentation the soils have intergrade properties between maritime and continental antarctic such as cryoturbation and redoximorphism side by side with desert pavements and ahumic character soil properties were more sensitive to the variations in parent material than to the topographic position in the landscape

the weathering of volcanic tephra and how they impact histosol development an example from south east iceland abstract little is known about the impact of tephra deposits from explosive volcanic eruptions on soil formation and weathering processes in organic soils the weathering of tephra of basaltic and rhyolitic origin and their impact on icelandic histosols were studied through a combination of physical chemical and mineralogical analyses two sampling sites were selected according to the presence of the light coloured rhyolitic tephra from the oraefajokull eruption in 1362 ce and a dark coloured basaltic vei ivotn tephra from 1477 ce in the volcanically active area south of vatnajokull in south east iceland the determining factor of pedogenesis in the investigated histosols is the om but the influence of tephra and aeolian material from external sources must be taken into consideration the soils are the result of altered plant residues and volcanic material tephra and aeolian material plant remnants as well as the soil itself are protected from decomposition by the prevailing anaerobic conditions a low soil ph and the repeated addition of inorganic matter clay formation is low while metal humus complexes are predominant feo fed ratios indicated a generally low degree of weathering being higher close to the basaltic tephra the mineralogy was dominated by plagioclase and pyroxene with quartz and zeolite as minor components in contrast to previous research on icelandic soils our investigations revealed layer silicates at both sites while we found evidence of smectite in the soils at kalfafell hydroxy interlayered minerals were found at reynivellir in the basaltic tephra traces of layer silicates could be verified in contrast the rhyolitic tephra did not show any pedogenic minerals suggesting that it had hardly altered since its deposition in 1362 ce it is not the chemical composition of the inorganic parent material but the location that may be an influencing factor on the formation of clay minerals in the investigated histosols

weathering of basaltic pebbles in a red soil from sardinia a microsite approach for the identification of secondary mineral phases abstract mineral weathering microsites in a basalt rock derived soil were investigated in the mediterranean environment of south western sardinia an in situ approach frequently used for saprolites and rock investigations was employed to examine the weathering microsites of a soil system this study compared clay phases that formed from the weathering of mineral bearing rock pebbles and soil crystal chemical composition with the goal of evaluating the evolutionary trends of the secondary minerals micromorphological mineralogical xrd and ft ir analyses and microscopic sem eds analyses were carried out on i plagioclase enstatite and glassy features weathered volcanic glass microsystems in rock pebbles embedded in the soil ii clay coatings microsystem connecting the soil rock environment and iii the soil itself eds data were plotted on phase diagrams to evaluate developmental and evolutionary trends of the weathered products the weathering of enstatite and volcanic glass resulted in primarily fe bearing montmorillonites while a mixture of fe bearing smectite and kaolinite developed from plagioclases our results indicated formation of secondary phases in open microsystems where transfers of elements among primary minerals and glass occur by slow diffusion along the network of inter mineral micropores cracks that developed inside the soil rock pebbles acted as direct connections between microsystems and the soil environment clay and fe mn coatings deposited in the cracks are an indication of clay migration the mineralogy of these clay coatings was similar to that of the soil matrix and the fine clays since it is likely that the clay migration processes remain active in guspini soils the further mineralogical similarities of clay coatings and soil fine clays suggest that the transformation of fe smectites into k s mlms occurs in the clay phases during transport prior to deposition into the soil environment indeed the similar mineralogy of the in situ analysed soil matrix and fine clays the youngest soil fraction is interpreted as due to same soil processes suggesting stable environmental conditions in the guspini area

mineralogy of loess and volcanic ash eolian mantles in pacific northwest usa landscapes abstract eolian mantles consisting of quaternary loess holocene volcanic ash and mixtures of the two are prominent features of most landscapes in the inland pacific northwest region of the usa soils of the loess mantled palouse region of eastern washington and northern idaho exhibit regional mineralogical trends related to mean annual precipitation and age clay content increases and caco3 decreases from areas of lower to higher precipitation clay mica is the dominant clay mineral in soils formed in the youngest loess ca

stable positions of rigid objects in non coaxial flow a study in vorticity analysis abstract distortions of a homogeneous fabric which occur around rigid objects in rocks deformed by non coaxial ductile flow are useful to determine the sense of shear but also contain information on other aspects of the flow rigid objects in a non coaxial flow fall into two categories those which are permanently rotating and those which can reach stable positions at high finite strain the orientation of such immobilized objects with respect to eigenvectors of instantaneous flow is a function of the vorticity number of the flow the ratio of instantaneous stretches and the axial ratio of the object in naturally deformed rocks immobilized rigid objects may be recognized from the geometry of the surrounding fabric tails of recrystallized material around porphyroclasts in a mylonite rotate towards parallellism with the extensional eigenvector of the flow and the shape of tails reflects the rotational behaviour of the porphyroclast the axial ratio of immobilized porphyroclasts and their orientation with respect to the tails can theoretically be used to determine the vorticity number of the flow and deviations from isochoric plane strain in practice such an analysis is as yet difficult but a tentative example is given of the way in which the vorticity number can be calculated from a population of feldspar porphyroclasts in a quartzite mylonite from the french pyrenees

the role of climate and vegetation in weathering and clay mineral formation in late quaternary soils of the swiss and italian alps nteractions between climate and soil remain ambiguous particularly when silicate weathering and clay mineral formation and transformation rates are considered in relation to global climate changes recent studies suggest that climate affects weathering rates much less than previously thought here we show that the climate in the central european alps has a significant but indirect influence on the weathering of soils through vegetation the pattern of element leaching and mineral transformations is not only due to precipitation and temperature element leaching was greatest in subalpine forests near the timberline weathering is lessened at higher and lower altitudes vegetation therefore contributes significantly to weathering processes the highest accumulation of organic matter was found in climatically cooler sites subalpine range where the production of organic ligands which enhance weathering is greatest patterns of smectite formation and distribution had strong similarities to that of the elemental losses of fe and al r 0 69 p 0 01 or base cations r 0 58 p 0 05 higher precipitation rates and the production of organic chelating compounds in the soil promoted the appearance of smectites the relationship between climate element leaching fe al ca mg k na and smectite formation is strongly nonlinear and driven by the podzolisation process which is more pronounced near the timberline because of the bioclimatic constellation climate warming will probably in the future lead to a decrease in som stocks in the subalpine to alpine range because of more favourable conditions for biodegradation that would also affect weathering processes

basalt and rhyo dacite weathering and soil clay formation under subtropical climate in southern brazil abstract the mineralogy of highly weathered soils is dominated by kaolinite group clay minerals however in the highlands of southern brazil the subtropical climate mean annual temperature 15 c mean annual precipitation 1900 mm yr favored accumulation of organic matter and occurrence of 2 1 clay minerals the objective of this work was to compare the weathering of the two main rock types in the volcanic plateau in the rio grande do sul in southern brazil in order to consider soil fertility and sustainability in this intensively cropped area two weathering profiles were sampled on basalt and rhyo dacite at elevations ranging between 760 and 850 m a s l the soil minerals were analyzed by x ray diffraction chemical extractions and ftir spectroscopy weathering intensity was inferred from bulk chemical analyses and calculation of weathering indices chemical index of alteration cia weathering intensity scale wis and elemental mass balance mineralogy was dominated by kaolinite and crystalline iron and aluminum oxy hydroxides and 2 1 clay minerals the surface horizons contained hydroxyl al interlayered minerals originating from aluminization of smectite present in the saprolite under acidic conditions with the important accumulation of organic matter results of mass balance calculation showed extensive loss of all elements high 4si wis and cia with residual accumulation of fe and al oxy hydroxides the degree of weathering is higher on rhyo dacite compared to basalt although rhyo dacite rock is richer in sio2 given the importance of 2 1 clay minerals on soil properties e g sorption aggregation a better understanding of their formation and transformation according to geochemical conditions is a key issue in the management of these sub tropical soils

the development of δ clasts in non linear viscous materials a numerical approach abstract winged porphyroclasts are often used as kinematic or strain indicators in shear zones in particular it has been suggested that the geometry of clasts in mylonites can give information about the rheological behaviour of the matrix around the clast passchier et al 1993 we tested this hypothesis with a numerical finite element simulation of the flow field of a viscous matrix around a relatively rigid clast power law viscous flow properties of the matrix with stress exponents of 1 linear viscous 3 and 5 were tested as well as three different sets of approximately simple shear boundary conditions which are relevant to experimental and or natural situations the simulations show that the flow field is primarily determined by the boundary conditions the stress exponent is of secondary importance in general the different boundary conditions produce two types of flow fields about the rigid clast an eye shaped flow field and a bow tie shaped flow field the former is produced by boundary conditions that approximate simple shear applied at an infinite distance from the rigid clast and the latter is produced by boundary conditions which are equivalent to a shear box or ring shear apparatus although both the shear box and ring shear boundary conditions produce bow tie flow patterns the wing geometries which result from the flow patterns for these two cases can be significantly different the geometry of the wings that develop on a clast is a direct function of the flow field around the clast for linear and non linear rheologies only the ring shear boundary conditions produce wings that show stair stepping i e wings that are parallel but not in the same plane in natural shear zones clasts both with and without stair stepping are observed in comparing geologic observations with experimental or numerical modelling it is essential to understand which boundary conditions are appropriate

basalt weathering and pedogenesis across an environmental gradient in the southern cascade range california usa abstract basalt rocks occupy substantial land area and play a significant role in global weathering patterns and biogeochemical cycling the objective of this research was to quantify climatic controls of weathering and pedogenic processes on basalt derived soils across an environmental gradient on the western slope of the casacade range of california usa we hypothesized that climate controls mineral neogenesis with cool moist conditions favoring formation of short range order sro materials and warm dry conditions favoring smectite crystalline fe oxyhydroxides and kaolins four pedons were sampled across an elevation gradient 250 2500 m having large variation in mean annual soil temperature 5 17 c and mean annual precipitation 750 1350 mm the soil mineral assemblage was characterized by x ray diffraction selective dissolution total elemental analysis and light microscopy the degree of weathering and mineral assemblage exhibited a clear threshold at the permanent winter snowline 1200 m maximum soil development was noted just below the snowline with soils dominated by kaolinite and dehydrated halloysite crystalline fe oxyhydroxides 48 kg m 2 extensive loss of cations chemical index of alteration cia 95 and clay accumulation 447 kg m 2 in contrast the high elevation snow dominated pedons displayed less intense weathering e g cia

first evidence for the presence of andisols in the dry hot environment of the arabian shield abstract saudi arabia has many volcanoes and extensive basaltic lava fields known as harrats located along the western part of the arabian shield sub parallel to the red sea the soils developed on these volcanic materials have not yet been investigated forty representative soil profiles were selected from six harrats and their morphological and physicochemical properties as well as their mineralogical compositions were characterized using standard chemical xrd sem and tem techniques the main objective of this study was to determine if the soils developed from basaltic rocks in the harrats of the arabian shield are andisols the results revealed that all representative profiles had volcanic glass content that ranged from 15 to 40 p retention capacity 35 and acid oxalate extractable a1o 1 2 feo that ranged from 0 44 to 2 20 the crystalline clay minerals were dominated by smectite kaolin kaolinite halloysite and mica illite whereas chlorite hydroxy interlayered vermiculite ch hiv palygorskite ca zeolites and pseudo chlorite were present as minor components small amounts of allophane imogolite and ferrihydrite made up the poorly crystalline clay minerals all representative profiles satisfied the criteria for andic soil properties and were classified as torrands due to the presence of an aridic soil moisture regime in the area paleoclimatic conditions that existed in the arabian peninsula over the last few thousand years are consistent with the formation of andic and or vitric soil properties because of this andisols developed from pyroclastic parent materials and are now present in dry hot conditions the presence of andisols in the study area was demonstrated and was mainly attributed to the influence of pleistocene paleoclimatic conditions

industrial mineral occurrences associated with cenozoic volcanic rocks of sardinia italy geological mineralogical geochemical features and genetic implications the most important industrial mineral im deposits associated with the cenozoic volcanics of sardinia include kaolin bentonite and zeolites though of less significance perlite and potassium feldspar are also important in local and national markets bentonite and to a lesser extent kaolin and perlite form economically viable deposits and zeolites appear as very important industrial mineral commodities for future economic development the market situation for potassium feldspar is still under evaluation for use in ceramics all these deposit types occur as alteration products of cenozoic volcanic rocks which were emplaced during three main volcanic cycles in the eocene ec 55 to 51 ma oligocene miocene omc 32 to 13 ma and pliocene pleistocene ppc 5 to 0 1 ma kaolin bentonite zeolites and potassium feldspar occur as alteration products of the omc volcanites perlite occurs as an alteration product of the ppc volcanites all deposits have generally derived from the alteration of the most acidic members of the cenozoic volcanic rocks rhyolites to rhyodacites but differences among the associated ore forming phenomena are recognized hydrothermal sensu stricto deuteric alteration and weathering are the most important processes involved in ore formation weathering although of minor importance can also contribute to enhance the alteration of the deposits formed by hydrothermal and deuteric processes the extent and type of occurrences are mainly controlled by the local geological and structural features and the environmental geochemical conditions kaolin occurs in three main districts at romana and tresnuraghes it is hosted within ignimbritic sequences while at serrenti furtei it is found in pyroclastic flows and ash flow tuffs kaolin formed by hydrothermal processes occurs in high sulfidation romana and serrenti furtei and low sulfidation tresnuraghes type epithermal systems the alteration is proximal to the feeder conduits and structural setting controls kaolin formation bentonite is widespread throughout sardinia deposits occur as stratiform mineral bodies in situ altered within poor welded pumice rich and ash rich layers and also as distal fall out deposits as lenticular bodies interlayered within the miocene sedimentary sequences the former originated by deuteric alteration and formation is mainly controlled by lithology whereas the second type originated by weathering which altered the volcanic ash lenses deposited in lacustrine and or fluvial deltaic environments

regional paleoprecipitation records from the late eocene and oligocene of north america abstract the marine 18o record indicates precipitous cooling or significant expansion of antarctic ice volume across the eocene oligocene epoch boundary at 33 7 ma this climatic step is also found in estimates of decreased paleoprecipitation from paleosols in oregon montana and nebraska but is only a part of a long term decline across the eocene oligocene transition rather than a sudden shift this suggests that climate was driven by a gradual process rather than a single perturbation paleoprecipitation levels stabilized during the oligocene coincident with a stabilization in 18o values possibly indicating a new climatic steady state

strain and kinematic analysis in general shear zones we present a unifying theory for the development and distribution of strain markers and kinematic indicators in zones of general shear and thus provide a framework in which data previously considered contradictory may be understood rigid and deformable porphyroclast systems including and complex grains are potential indicators of both strain and flow the shapes and distribution of such porphyroclast systems may be used to distinguish among different tectonic regimes general shear is divided into two fields sub simple shear in which the rotational component of the strain is less than that for simple shear and super simple shear in which the rotational component is greater than for simple shear sub simple shear may involve narrowing or broadening of shear zones super simple shear regimes are possible in local regions such as the vicinities of deformable porphyroclasts but must be enclosed by regimes of sub simple shear the polar mohr constructions for finite deformation and flow are useful to analyze general shear in theory the hyperbolic net is employed for practical plotting of real data and derivation of the kinematic vorticity number wn this number represents the relative contributions of pure and simple shear in steady flow in nature deformation is thought to build up and decay by processes that may invalidate the assumption of constant flow regime we therefore introduce the concept of accelerating deformation and analyze the implications of non steady flow for the shearing histories of deformed objects

experimental modelling of mantled porphyroclasts abstract mantled porphyroclasts are commonly used as sense of shear indicators in mylonites analogue experiments have been carried out to model the development of such objects rigid spheres mantled by a viscous plasticene putty mixture with power law behaviour were suspended in an optically transparent newtonian polymer matrix the samples were deformed between two cylinders one placed within the other and with coinciding axes this induces a non coaxial flow between the cylinders and allows the achievement of high finite strain the viscous mantle around the rigid sphere remained undeformed deformed into an ellipsoid or developed wings the final geometry depends mainly on the induced viscosity contrast between the mantle and the matrix which is a function of the flow induced stress on the surface of the mantle winged mantles only develop if the induced viscosity contrast between the mantle and the matrix polymer is sufficiently small if this critical induced viscosity contrast is exceeded the mantled sphere remains undeformed or obtains a stable ellipsoidal shape even at high finite strain shaped winged mantles only develop in simple shear flow if the mantle around a rigid sphere is thin

zeolites in soil environments the limited occurrence of these minerals has resulted in a scant knowledge about their properties in the soils zelazny and calhoun 1977 as pointed out by the above authors the occurrence of natural zeolites in soils is rare and not well known and only about 75 papers have been published describing the occurrence of zeolites in soils these occurrences range from hot humid soils in india to cold arid soils in the dry valleys of antarctica most of these reports describe residual zeolite phases that have persisted from the parent material during soil formation however there are reports of zeolites that have formed in soil environments a variety of natural zeolites have been found in soils including analcime chabazite clinoptilolite gismondine laumontite mordenite natrolite phillipsite and stilbite over the past 25 years natural zeolites have been examined for a variety of agricultural and environmental applications because of their unique cation exchange adsorption and molecular sieving properties and their abundance in near surface sedimentary deposits natural zeolites have been used as soil conditioners slow release fertilizers carriers for insecticides and herbicides remediation agents in contaminated soils and dietary supple ments in animal nutrition ming and allen this volume pond 1995 these applications can result in direct or indirect incorporation of natural zeolites into soils if these minerals are to be used effectively in these applications it will be necessary to understand the long term stability and effects of zeolites in soils or soil like systems several reviews have been published on the occurrences and properties of zeolites in soils zelazny and calhoun 1977 ming and dixon 1987c ming and dixon 1988 ming and mumpton 1989 boettinger and graham 1995 this chapter provides an overview and update on the occurrence of zeolites in soils and briefly describes methodology used for identifying and characterizing zeolites

clay mineralogy and its relationship to soil solution composition in soils from different weathering environments of humid asia japan thailand and indonesia abstract we studied the relationship between the clay mineralogy of subsurface soils from 204 sites and their water extracts in upland soils of humid asia japan thailand and indonesia to understand their formation the clay minerals were identified by xrd and the kaolin minerals and gibbsite were quantified with dta their thermodynamic stability was related to the ion activity of soil water extracts in soils on mica free andesitic or mafic parent material kaolin minerals and smectite dominated in all regions among mica containing soils derived from felsic or sedimentary rocks mineralogical and soil solution compositions indicate that in thailand mica was stable at high ph 5 4 6 5 whereas in soils from japan and indonesia mica turned into hydroxy al interlayered vermiculite hiv or vermiculite at lower ph 4 3 5 5 in japanese soils hiv and gibbsite form under high activity of al oh species in contrast the low activity of al oh species in indonesian soils resulted in the dissolution of al hydroxides between 2 1 layers and gibbsite and the dominance of kaolin minerals and vermiculite we conclude that three factors play an important role for the clay mineralogy in humid asia the nature of parent material i e presence or absence of mica soil ph as affected by precipitation and evapotranspiration and activity of al oh species in soil solution reflecting soil age