Changes In Clay Mineralogy Research Articles

ABSTRACT: Changes in Clay Mineralogy and Fabric Development Across Selected Fault Zones

ABSTRACT: Changes in Clay Mineralogy and Fabric Development Across Selected Fault Zones

Rapid clay transformations in Delaware salt marshes

Salt marshes are the major areas for net sedimentation in many estuaries such as the Delaware Bay, and their diagenetic chemistry is harsh and extreme with large seasonal excursions in chlorinity (1–50 ppt), pH (4–6), and Eh (−240+120). Such diagenesis is driven by organic matter decomposition using redox cycles of S and Fe materials imported primarily as tidal sea water SO 4 and Fe silicates, respectively. Important and quantitative changes in clay mineralogy occur within a decade at the redox boundary in a high marsh sediment near Lewes, Delaware. The clay mineralogy consists initially of a micaceous illite and chlorite mixture accumulating at the salt marsh surface. It is comprised of relic glacial sediments deposited on the continental slope during their net tidal movement from the sea to land. Once buried, these detrital clays are transformed into a new assemblage containing an illite/smectitic mixed layer mineral of poor crystallinity. Using curve decomposition techniques on complex X-ray traces, it is estimated that this new phase constitutes 45–55% of the clay fraction. The redox boundary where the sharp transition occurs is only about 20 a old as determined by 210Pb and 137Cs geochronology, and, thus, the clay mineral transformation is rapid. The occurrence of the new, abundant clay mineral is very abrupt (less than 1 cm at 12 cm in depth) and, thus, may itself occur in as little as three years. Once formed, the new mixed layer phase remains stable during the subsequent 40 a of burial from the time of formation at the oxic/anoxic boundary. Slow transformations of unstable primary clay reactants such as illite and chlorite are a common process of soil formation. However such rapid clay reactions have rarely been documented in either subaerial or submerged soil settings. The formation of a smectite mineral product of high chemical reactivity for a significant portion of the clays in a soil is unusual. In fact, the abrupt change in clay mineralogy in the salt marsh occurs precisely at the sharp evolution in salt marsh geochemistry from oxidized to reducing conditions where there is extensive redox cycling of Fe and S phases. A large seasonal oscillation in interstitial pH and Eh probably contributes to the rapid clay transformation. Such clay transformations may have important implications for the retention of other trace elements entering the salt marsh by atmospheric fallout and tidal cycles, or the release of such metal inventories after burial.

Provenance change coupled with increased clay flux during deglacial times in the western equatorial Atlantic

In the western tropical Atlantic, decreases in the percentage of calcium carbonate in marine sediments are concurrent with increases in clay accumulation rates. In cores with records of percent carbonate extending well back into the Pleistocene, a series of low-calcium carbonate events can be seen. Existing 14C geochronology allows the timing of the uppermost low-carbonate event to be constrained to the last deglacial interval and suggests a relatively short duration between about 16 and 14 ka BP ( 14C), although more dating is needed to confirm the time limits. The bulk compositional changes of the upper low-calcium carbonate zones correspond to changes in clay mineralogy and in Sr isotope composition of the detrital clay fractions. In four cores the kaolinite/chlorite ratio varies systematically along a 1800 km NW–SE transect, starting with low kaolinite/chlorite and low 87Sr/ 86Sr ratios at the west end of the Vema fracture zone (core RC16-55) and ending with high kaolinite/chlorite and high 87Sr/ 86Sr ratios at the west end of the Romanche fracture zone (core V26-99). The kaolinite/chlorite ratio and Sr isotopic compositions from several samples in these cores also show a positive co-variation. The changes in composition within the low-carbonate interval correspond to changes in contributions of young, relatively unweathered (Amazon) and old, highly weathered (Rio Sao Francisco) sources. The provenance pattern allows that this pulse of clay deposition is reasonably interpreted to be a climate signal that could represent increased rainfall in tropical South America during the deglaciation, consistent with published oxygen isotope data from the Amazon fan. However, there are published carbonate records from near Africa that appear to show a correlative clay-rich layer. Thus, an alternative hypothesis is that the gray clay layer could reflect a plume of sediment stirred up from the shelf break during sea level rise associated with deglaciation.

Environmental magnetic record of Antarctic palaeoclimate from Eocene/Oligocene glaciomarine sediments, Victoria Land Basin

SUMMARY The onset of continent-wide glaciation in Antarctica is still poorly understood, despite being one of the most important palaeoclimatic events in the Cenozoic. The Eocene/ Oligocene boundary interval has recently been recognized as a critical time for Antarctic climatic evolution, and it may mark the preglacial‐glacial transition. Magnetic susceptibility, intensity of natural and artificial remanences, hysteresis parameters and magnetic anisotropy of the lower half (late Eocene/early Oligocene) of the CIROS-1 core (from McMurdo Sound, Antarctica) reveal alternating intervals of high and low magnetic mineral concentrations that do not correspond to lithostratigraphic units in the core. Pseudo-single-domain magnetite is the main magnetic mineral throughout the sequence, and sharp changes in magnetite concentration match changes in clay mineralogy beneath and at the Eocene/Oligocene boundary. The detrital magnetite originated from weathering of the Ferrar Group (which comprises basic extrusive and intrusive igneous rocks). Weathering processes and input of magnetite to the Victoria Land Basin were intense during periods when the Antarctic climate was warmer than today, but during intervals when the climate was relatively cool, chemical weathering of the Ferrar Group was suppressed and input of detrital magnetite to the Victoria Land Basin decreased. Our results also indicate that a cold and dry climate was not established in Antarctica until the Eocene/Oligocene boundary, with major ice sheet growth occurring at the early/late Oligocene boundary. Some earlier cold intervals are identified, which indicate that climate had begun to deteriorate by the middle/late Eocene boundary.

Fine silt and clay mineralogical changes of a soil chronosequence in the Langtang valley (Central Nepal)

AbstractChemical and mineralogical properties of a soil chronosequence in the high mountain zone between 3857 m and 4120 m a.s.l. in Central Nepal (Langtang valley) are presented. The soils have been developed in moraine deposits which consist of acid gneisses. They were classified as Entisols, and Spodosols. XRD analyses of the clay and fine silt fraction show increasing changes with distance from the recent Lirung glacier, depending on the time of deposition, resp. soil age. Alteration of illite to interstratified minerals and to hydroxy‐Al interlayered minerals or pedogenic chlorite with increasing soil development could be observed. The interstratified minerals could be identified as random and regular illite‐interlayered vermiculite mixed‐layer minerals. Intensification of the X‐ray signals of the fine silt fraction is given compared to the clay. With increasing soil development differences between the clay and fine silt fraction seem to increase. Indications are given of interstratification of the mica‐pedogenic chlorite and chloriteinterlayered vermiculite type in the more intensively weathered soils.

Palaeoclimatic significance of changes in clay mineralogy across the Jurassic-Cretaceous boundary in England and France

Clay mineralogical changes across the Jurassic-Cretaceous boundary from the northern to the southern part of western Europe show similar patterns in: the mudrocks exposed on the Yorkshire Coast, the paralic sediments of the Dorset Wessex Basin, and the Jura and Vocontian Trough of S.E. France, This comprises a change from smectite-poor sediments in the Jurassic (with correspondingly abundant illite and kaolinite) to sediments with abundant smectite in the Jurassic-Cretaceous boundary beds, depleted in kaolinite. This change occurs in the Oxfordian in the south, to? latest Volgian in the north of the study area. Kaolinite reappears in abundance in the late Ryazanian or stratigraphic equivalent in all the locations studied. Comparison with other climatic indicators and other areas suggest that these variations can be ascribed to a phase of latest Jurassic-earliest Cretaceous aridity, the onset of which appears to be diachronous across W. Europe. Possible causes for the climatic change towards aridity are examined: the orographic effect of mountains or plateaus to the east of the study area is considered most likely.

Mapping Surface Alteration Effects Associated with Hydrocarbon Reservoirs at Gypsum Plain, Texas, and Cement, Oklahoma, Using Multispectral Information

Two test sites, Gypsum Plain, Texas, and Cement, Oklahoma, were selected to evaluate combined use of airborne visible/infrared imaging spectrometer (AVIRIS) and thermal infrared multispectral scanner (TIMS) for detection of alteration effects associated with hydrocarbon microseepage. Bleaching of redbuds, variations in carbonate cement, replacement of gypsum, exidation of iron, and changes in clay mineralogy may correlate spatially with oil and gas production and subsurface structures. Spectral features due to iron oxides, calcite, gypsum, smectite, and kaolinite can be mapped using AVIRIS image data, using various techniques such as ratios, scene-dependent log residuals, and scene-independent radioactive transfer approach using LOWTRAN7, and with TIMSA data using DSTRETCH. Poor signal-to-noise in the 2.0-2.4 {mu}m region limited the ability to map clay, gypsum, and carbonates both at Cement and Gypsum Plain, carbonate and quartz-rich sediments at Gypsum Plain, and differentiated soils developed on the Rush Spring Sandstone from soil derived from the Cloud Chief Formation at Cement. Combined spectral and photogeologic interpretation of coregistered AVIRIS, TIMS, and Landsat TM, and digital elevation data demonstrate the practical approaches for surface oil and gas exploration using presently operational commercial aircraft and future satellite systems.

Effect of rainfall on pedogenesis in a climosequence of soils near Lake Pukaki, New Zealand

Abstract Four soils were sampled along a 42 km transect near Lake Pukaki, South Island, New Zealand, to study the physical, chemical, and mineralogical changes that have occurred under mean annual rainfalls of 640 mm at profile 1 to 2000 mm at profile 4. Sampling sites were chosen to minimise difference in soil-forming factors other than rainfall. All soils were formed in loess, ranging in thickness from 40 to 76 cm, over till. The marked differences found in soil properties of the four profiles illustrated the major effect rainfall has in determining the rates of leaching, weathering, and podzolisation. Leaching of bases, acidity, and exchangeable aluminium were found to increase markedly with rainfall. The main differences occurred between profiles 1 and 2, which reflected the marked soil moisture deficit and low soil water surplus characteristic of profile 1. A progressive increase in weathering was shown by increasing profile development and clay content with rainfall, by increasing conversion of total aluminium and iron to readily extractable forms, and by changes in clay mineralogy. Soil profiles showed progressive development of podzol morphology with increasing rainfall. Horizons identified in profile 1 mainly reflected accumulation of organic matter and weak weathering whereas profile 4 had a distinct eluvial horizon and evidence of accumulation of sesquioxides and humus in B horizons. This trend of increasing podzolisation was substantiated by chemical evidence.

TRANSFORMATION OF VERMICULITE TO PEDOGENIC MICA BY FIXATION OF POTASSIUM AND AMMONIUM IN A SIX-YEAR FIELD MANURE APPLICATION EXPERIMENT

In a field experiment in which heavy applications of liquid dairy manure were added annually for 6 yr to a vermiculite-containing corn-cropped sandy clay loam soil (Mountain series), fixation potential and X-ray diffraction analyses were done to determine if fixation of added K+ and NH4+ had occurred and clay mineralogical changes could be detected. Of the 850 kg K+ and the 460 kg NH4+ added per hectare each year, approximately 28% of the K+ and 24% of the NH4+ remained fixed. This caused a marked increase in the 1.0-nm peak at the expense of the 1.4-nm peak due to collapse of vermiculite layers to form pedogenic mica. Thus, changes in soil management, specifically in fertilizer practices, can result in significant changes in clay mineralogy within a short period of time. Such changes are agronomically important and should be taken into account in the interpretation of clay mineralogical data. Key words: Potassium and ammonium fixation, vermiculite to pedogenic mica transformation, liquid manure application

Changes in clay mineralogy in a chronosequence of polder paddy soils from Kojima basin, Japan

Changes in the clay mineralogy in a chronosequence of polder soils cultivated with paddy rice for 15, 75, 150, and 265 years in Kojima Basin were studied. Parent materials of each profile appeared to be homogeneous. Prolonged paddy cultivation (150 and 265 years) brought about some modification in the clay mineralogy of Ap horizons, while the mineralogical changes were not evident in the profiles less than 75 years of age. Characteristic changes consisted of the formation of 18-25 Å minerals, which were composed of interlamellar humus-smectite complexes and interstratified minerals. The interstratification showed intermediate stages from smectite to kaolin minerals along with partial chloritization of smectite. The interstratification and partial chloritization of smectite caused the CEC of the clay fractions of Ap horizons to decrease partly.

Soils on Terraces Along the Cauca River, Colombia: II. The Sand and Clay Fractions

AbstractMicroscopic examination and elemental analyses of the sand fractions of the terrace soils show that their compositions are too variable to infer anything very noteworthy about the relative rates of primary mineral weathering. However, the parent materials are sufficiently uniform to reveal a relatively continuous progression of notable changes in clay mineralogy from floodplain through the age sequence of terrace soils. Mica, chlorite, vermiculite, smectite, and kaolinite are present in appreciable quantities in the floodplain soils and mica is present in the sand fractions of all terrace soils, but of these only kaolinite is present in more than minute amounts in the sola of any terrace soils. The quantities of 14A minerals with interlayer Al are greatest in the sola of the youngest terrace soils, but they persist in somewhat reduced quantities throughout all except in the subsoil on the highest terrace. Both amorphous aluminosilicates and gibbsite reach maximum concentrations in the lower terrace soils, thence their quantities decline with increasing age. The Feo/Fed ratio has a similar age trend but peaks sooner, at 0.53 in the higher floodplain soil, and thence decreases steadily with soil age to < 0.01 in the clay fraction of the highest terrace soil. Kaolinite is the major constituent of clay in the sola of all terrace soils. It increases with soil age to approximately 60% of the clay fraction in the highest terrace soil.

Clay mineral distribution patterns as influenced by depositional processes in the Southeastern Levantine Sea

ABSTRACTAnalysis of the clay minerals in stratigraphically defined cores (23,000 years BP to the present) in the southeastern Levantine‐Nile Cone sector of the eastern Mediterranean indicates that depositional processes are very significant in determining the distribution of clay assemblages. The interplay of long‐distance transport by water mass circulation, downslope mass gravity transport and wind dispersal is recorded by the clay assemblages in each of the stratigraphic layers. The temporal variations and spatial distribution of smectite, the dominant clay mineral of the River Nile, can be related closely to downslope gravity‐related processes and to deposition from water mass flow. Increased kaolinite, in part of wind‐blown origin from North Africa, correlates with areas receiving low terrigenous input but influenced by enhanced suspended sediment transport. Illite and chlorite distributions are most closely associated with a northern Levantine provenance and dispersal by the circulation of eastern Mediterranean water masses. Climatically induced changes may have altered the clay minerals in the region and minor diagenetic changes may have occurred, but these factors do not fully explain observed vertical clay mineral changes in the Late Quaternary. We conclude that palaeoclimatic interpretations based on vertical clay mineralogical changes at single core localities should be approached cautiously in small ocean basins such as the Mediterranean.

Distribution and Composition of Suspended Sediment in the Bottom Waters of the Washington Continental Shelf and Slope

ABSTRACT In order to study the dispersal of river-borne suspended sediments through the marine environment, suspensate samples were collected at 26 stations from the lower Columbia River and bottom waters of the adjacent continental shelf and slope during the summer and early fall of 1971. X-ray diffraction analysis has shown the montmorillonite/chlorite (M/C) ratio to be a useful indicator of Columbia River-derived sediments. M/C values vary from high (> 1.0) in the Columbia River and shelf bottom waters, through moderate (0.96-0.65) in the head and upper reaches of three major submarine canyons on the slope, to low (<0.48) in samples from the distal portions of the canyons and the open slope areas between the canyons. These trends appear to develop from physical sedimentary processes, such as differential sedimentation and resuspension, which result in a continually changing clay mineral composition of the Columbia River suspended load as it diffuses into the coastal ocean environment. There is no evidence to indicate that these changes in clay mineralogy are due either to dilution of the Columbia River suspensate by other continental or marine sources, or transformation of the clay minerals due to reactions with seawater. Comparison of the M/C values of the suspended sediment with surficial bottom sediment collected at the same stations indicates that naturally occurring differences between the two can be falsely exaggerated if similar particle size ranges are not used in each analysis. Agreement of the clay mineral trends is best when comparing the M/C ratios of the total inorganic suspended sediment to the M/C ratios of the 0-62µ, rather than the 0-20µ or 0-2µ, fraction of the bottom sediments.

Weathering of the Sioux Quartzite Near New Ulm, Minnesota, as Related to Cretaceous Climates

ABSTRACT An exposure of Precambrian Sioux Quartzite near the city of New Ulm, Minnesota, shows evidence of intensive chemical weathering. The silica cement matrix material of the quartzite has been removed and the argillaceous part (probably sericite) of the cement matrix has been altered to kaolinite. The regolith is composed of loose pink sand with a kaolin clay matrix and is as much as 20 feet thick. The regolith probably is no younger than Early Cenomanian and in part may be correlated with the Van Bibber Shale Member and older members of the South Platte Formation of Albian age in Colorado. Upper Cretaceous sedimentary rocks consisting primarily of red and green shale, siltstone, and sandstone overlie the weathered quartzite. Illite and montmorillonite are the principal clay minerals in these rocks, with kaolinite present in minor amounts. The significant change in clay mineralogy, coupled with paleontological evidence, indicates a pronounced change in climatic conditions during Cenomanian time. The humid tropical climate with good drainage conditions which was conducive to kaolinite formation was replaced by a temperate climate with poor drainage. The principal clay minerals incorporated in the sedimentary rocks formed after the climatic change are illite and montmorillonite. The illite may have been derived from erosion of older illite-bearing rocks and/or from chemical weathering of the silicate minerals in these rocks. The montmorillonite may have been formed by the alteration of volcanic ash from sources lying to the west. It is therefore possible to distinguish rocks formed before and after the climatic change on he basis of clay mineralogy. The Sioux Quartzite stood as a highland during the formation of the kaolinitic regolith and shed its weathering products into topographically lower areas. The quartz sand produced from the quartzite was reworked by streams flowing to seas lying to the west and now makes up a large part of the Dakota Formation of Minnesota. Glacial erosion during Pleistocene time removed most of the weathered zone from exposures of the Sioux Quartzite, but bleached joints, or the roots of the weathered zone, remain as evidence of the past humid, tropical conditions.

Clay-Mineral Diagenesis in Atoka (Pennsylvanian) Sandstone, Crawford County, Arkansas: ABSTRACT

Chemical and mineralogic evidence indicates significant clay-mineral diagenesis in a shallow (237 ft) core of Atoka (Pennsylvania) sandstone from Crawford County, Arkansas. This core spanned a complex sequence of interbedded sandstone and shale that is at least partly marine. Clay shales are dominated by illite with significant amounts of kaolinite and minor amounts of chlorite. Increasingly sandy shales contain progressively more chlorite and less kaolinite; illite remains the dominant clay-mineral component. The clay fractions (< 2µ) of sandstones are dominated by chlorite with lesser amounts of illite and no kaolinite. The strong contrast between the clay-mineral contents of these closely interbedded sandstones and shales suggests a diagenetic change that occurred primarily in the sandstones because of their greater permeability. The chlorite of the sandstones most likely has been formed authigenically with concurrent destruction of kaolinite. Elimination of kaolinite from sandstones by differential sedimentation seems unlikely because (1) it is doubtful that natural mechanical processes could produce the perfect separation of kaolinite found in these rocks, and (2) numerous studies of Recent and ancient sediments indicate that kaolinite commonly is concentrated in sandstones rather than eliminated from them. Clay-mineralogical changes in the sandstones may be part of an overall pattern of diagenesis in an alkaline, reducing environment that also included the formation of siderite rhombohedra and significant solution of silica (as indicated by straight or embayed contacts of quartz grains). Much of the discussion on the origin of clayey sediments in modern deposits has been devoted to the relative importance of provenance versus environmental End_Page 552------------------------------ alteration or segregation. With respect to ancient deposits, however, approaches confined to these factors are inadequate where diagenesis of clay minerals has occurred, as it apparently has in the Atoka sandstone and sandy shale. End_of_Article - Last_Page 553------------

Effect of Source and Environment on Clay Minerals

The clay mineral assemblage in an area of active deposition is dependent largely on the character of the source area. This conclusion is based on a study of the clay mineralogy of sediments of the lower Mississippi River, the active delta region, the St. Bernard Sub-delta, and the Mississippi Sound-Mobile Bay area. Montmorillonite, the predominant clay mineral in the Mississippi River and Delta sediments, is apparently the stable product of soil development and rock weathering in the drainage basin of the Mississippi River. The sediments of the Mississippi Sound-Mobile Bay area, east of the Mississippi Delta and derived ultimately from the Appalachian Province, contain considerably more kaolinite. Transition zones between the two sediment types can be differentiated. Alteration of clay minerals in a depositional area can be expected where the sedimentation rate is low and sufficient time is available for chemical equilibria between the sea water and the clay minerals. In areas of rapid mud deposition, the blanketing effect of overlying clay material probably reduces the chemical interaction to that which is possible between the clay and the entrapped water. The Mississippi River sediment carried into the saline environment, does not show significant changes in clay mineralogy except along the shelf edge. In this area of slow sedimentation, illite (clay mica) is more prominent. In the St. Bernard Sub-delta, a non-active depositional area for the last 400 years, alteration or diagenesis of the contained clay minerals appears to be associated with evidence of exposure of the sediment to surface oxidizing conditions. In the Mississippi Sound-Mobile Bay area the clays alter rapidly upon entering the saline environment. A part of the clay mineral assemblage has been attributed to a montmorillonite-organic complex, which appears to be modified or destroyed in the alkaline sea-water environment. An examination of buried muds of Tertiary age has indicated that little or no alteration of clay minerals takes place in shales to a depth of several thousand feet. However, clay minerals contained in sands may be greatly altered during burial.