Mica In Soils Research Articles

K-Ar Age Constraints on the Origin Of Micaceous Minerals in Savannah River Site Soils, South Carolina, USA

AbstractK-Ar measurements were used in this study of upland Savannah River Site soils to distinguish between sorbed K and the K remaining in remnants of primary minerals. Study of sorbed K contributes to understanding further the interaction of alkali metals (Cs in particular) with the soils. Primary mineral K and the associated radiogenic Ar were studied to characterize soil mica with respect to its provenance and its relationship to hydroxy-interlayered vermiculite. K-Ar age values of Na-saturated clay fractions from five samples of these soils range in age from 270 to 370 Ma. After a moderate acid treatment (6% HNO3 v/v, ~1 mol dm-3, 3 h, 80°C) of the clay fractions, K-Ar age values (270-325 Ma) were little changed on the whole, but they were more closely grouped near 300 Ma. Earlier work had shown that most of the K in these soils is found in material resistant to moderate acid extraction. The K-Ar age values show that this acid-resistant material is much older than any pedogenic minerals could be, even much older than the sedimentary parent rocks from which the soils were derived. These observations support earlier inferences by others that the K in these well leached soils is largely in remnants of primary muscovite from the parent sediments. Age values near 300 Ma suggest that the muscovite is largely from proximal Piedmont terranes of the Appalachian orogen, where the K-Ar relationship in most micas was set by Alleghanian tectonic processes late in the Paleozoic Era. The structural location of the K within mica, shown by the retention of the associated radiogenic Ar, is in contrast to the sorption-dominated behavior of the Cs and most of the Rb in these soils during pedogenesis. Stronger acid treatment (~6 mol dm-3 HNO3, 3 h, 100°C) extracted substantial fractions of both the K and the radiogenic Ar from bulk-soil portions, indicating destruction of some of the primary mica. K-Ar age values for the sand-rich bulk soils were not useful for this study because the sand contains excess radiogenic Ar, probably in sand-sized vein quartz.

Role of weathering of fine-grained micas in potassium management of Indian soils

Although the major soils of India (alluvial, ferruginous and black soils), endowed with fine-grained micas, are known as natural K suppliers to plants, crop response to K fertilizer treatment has been anomalous. The silt and clay fractions of 14 benchmark soils were subjected to repeated batch type Ba–K exchange to study the rate of K release. The significant positive correlation between cumulative K release in 25 extractions and X-ray intensity ratio of peak heights of the 001 and 002 basal reflections of mica in the silt ( r=0.629 at 1% level) and clay ( r=0.729 at 1% level) suggested that although the fine-grained muscovite and biotite co-exist in soils, the rate of K release and crop response to K are related primarily to the presence of biotite only while muscovite remains as an inert source of K in soils justifying the crop response to K fertilizers. Soil micas under a scanning electron microscope (SEM) indicated that biotite particles were generally thick, showing layer separation with bending at edges due to the formation of vermiculite around their rims. The muscovites, on the other hand, were characterized by very minor layer separation at their edges. To resolve the issue of layer separation of micas through the release of K during the formation of soils, experimental studies of repeated Ba–K exchange were conducted with specimen muscovite and biotite and also on the mixture of the two micas. Experimental studies indicated that at ambient temperature and pressure, muscovite released negligible amount of K from its exposed surfaces and the weathering of muscovite was inhibited in the presence of biotite. This confirmed the observation that when muscovite and biotite co-exist, muscovite hardly weathers in soil environments. Hence, its enrichment in soils does not enhance the supply of K. Therefore, weathering products like di- and trioctahedral vermiculite and smectite are generally the products of the weathering of biotite mica. The X-ray intensity ratio of 001 and 002 basal reflections of mica has been found to be an effective diagnostic parameter to find out the quality of mica and therefore to judge the K releasing potential of soils. However, actual quantification of fine-grained biotites of soils appears to be mandatory for the precise determination of K reserves in soils in order to predict release of K for sustainable K management.

Modeling Radiocesium Fixation in Upland Organic Soils of Northwest England

Two models of time-dependent 137Cs adsorption and fixation by soil were fitted to solution activity data from incubated organic upland soils, over a period of 709 days. Both model fits were highly (p < 0.01) or very highly (p < 0.001) significant. Both models differentiated between specifically adsorbed and nonspecifically adsorbed ‘labile' radiocesium. Transfer to a nonlabile pool was either by a kinetic step (model I) or a diffusive process (model II). Although fits for model II were comparatively worse in some soils, the second model had the dual advantage of being more mechanistic in structure and requiring fewer parameters. Parameters estimated for models I and II compared favorably with those derived experimentally; some dependence on soil mica was evident. Model I was used to predict the change in bioavail ability of radiocesium in soils following documented inputs from Windscale (1957), fallout from weapons testing (1960s), and the Chernobyl release (1986). For all but one of the five organic soils, long-term predic tions of relative bioavailability generated by model I were similar to the limited range of published values for 137Cs uptake by vegetation. It is concluded that the Cs fixation models presented account for a substantial part of the change in availability of 137Cs observed in field studies.

Isotopic evidence for the eolian origin of quartz and mica in soils developed on volcanic materials in the Canary Archipelago

Quartz and mica contents of soils developed on volcanic materials in the Canary Archipelago (Lanzarote, Tenerife, Gomera and La Palma islands), off western Africa are often higher in surficial horizons with higher rainfall and older landscape age. The soil quartz particles are fine-grained (less than 53 μm in diameter) and well-sorted. The oxygen isotopic abundance (δ 18O SMOW) of fine aerosol-sized quartz (1–10 μm in diameter) showed a range of +16.0 to +18.2%‰. The values are compatible with those of the same sized-quartz from two Holocene deep sea sediments in Cape Verde Rise (+16.0 and +16.1%‰) and Saharan dusts (+15.8%‰; La Laguna, Tenerife, +16.2%‰; Barbados, West Indies). A distinct 87Sr/ 86Sr ratio of 0.717 for a micaceous horizon from Lanzarote is comparable with those of Saharan dusts (0.715 to 0.721), but not with reported values (0.7032) from local volcanics. These geochemical parameters show that the fine-grained quartz together with mica in soils of the Canary Archipelago are transported from north African (Sahara) deserts by Trade Winds, and negate both possibilities of authigenesis and inheritance from weathering of local volcanics.

Potassium and magnesium in some Kenyan soils: their mineral sources and release to Ca‐resin

SUMMARYFive soil types from Kenya were examined for their ability to release K and Mg to crops by extracting them with a calcium‐saturated cation exchange resin, and for the mineral sources of K and Mg. Amounts and rates of release of exchangeable, short‐ and long‐term reserves of K and Mg were determined. This was done for K before and after one, two and 10 wetting and drying (WD) cycles, designed to mimic the effect of the local climate on K release. The order of decreasing K and Mg contents of the soils was Muguga &gt; &gt; Katumani &gt; Kampi‐ya‐Mawe (KYM) ∼ Ithookwe ∼ Kwale. In the case of K, wetting and drying increased the exchangeable fraction in all of the soils. The Muguga, Ithookwe and KYM soils have the capacity to release a great deal of K in the long‐term, but at very different rates; the Kwale soil has few reserves and fixes K on WD.The K and Mg contents of the soils were closely related to the mica contents of the clay + silt fractions. Exchangeable and non‐exchangeable K was released from soil micas primarily by ion exchange, with some contribution to non‐exchangeable K from dissolution. Release of exchangeable Mg was primarily by ion exchange, whilst that of non‐exchangeable matrix Mg was by dissolution of trioctahedral mica in the clay + silt and the sand fractions of the soils. Response would be expected only to K fertilizers and only with the Kwale soil. However, all the other soils should, in the interests of good husbandry, receive maintenance dressings of K and Mg at convenient times in the crop rotation.

Occurrence of High‐charge Beidellite in a Vertic Haplaquoll of Northwestern Minnesota

AbstractThe 2:1 layer silicate mineralogy of a Vertic Haplaquoll of north‐western Minnesota was studied using x‐ray diffraction and determination of cation exchange capacity (CEC). The x‐ray diffraction behavior of Li‐ and K‐saturated samples demonstrated that a highcharge smectite with tetrahedral charge dominates the mineralogy of both the coarse and the fine clay fractions. The high CEC and the large difference between Li‐CEC and K‐CEC confirmed the x‐ray results. Alkylammonium‐clay complex basal spacings show two phases of 2:1 clays; a high charge (about 0.9 molc per ½ unit cell formula) phase concentrated in the coarse clay and an Fe‐rich beidellite with a charge of 0.4 to 0.5 molc per ½ unit cell formula. The high charge phase largely represents K+ ‐depleted mica formed during the analytical procedure. This phase may also contain some soil vermiculite. The results presented in this study suggest that beidellite is a product of mica weathering, and that during weathering soil mica is transformed first to a vermiculite then to a beidellite, preserving the tetrahedral character of the charge.

THE NATURE OF SMECTITES IN SOME FINE TEXTURED LACUSTRINE PARENT MATERIALS IN SOUTHERN SASKATCHEWAN

Detailed mineralogy and chemistry of the clay fraction of five glacio-lacustrine deposits and of one Cretaceous marine shale (Ashville) were studied. Fine clay separates (&lt; 0.2 μm) of the five parent materials were predominantly smectite with an average chemical composition:[Formula: see text]X-ray diffraction, dehydration, infrared, and chemical analyses, and the Greene-Kelly test showed that the smectite was an iron rich montmorillonite. Similarities in the crystal structure of the five soil parent material clays suggest that they were likely transported from the same source. Despite the differences in percentage of clay minerals, similarities between chemical composition of the coarse and the fine clays is interpreted as an indication of close diagenetic relationships between the predominant smectite and soil mica. High silicate bound iron may have caused a distortion in the crystal lattice and a slightly favorable weathering condition of smectites. However, presence of high exchangeable and soluble magnesium in the soil complex is likely retarding the smectite alteration. Thus, weathering by elemental substitution may have been restricted to the smectite end member only. Key words: Swelling clay soils, iron montmorillonite, chemical composition of smectites, dehydration of smectites

Characterization of Morphological Features of Soil Micas Using Scanning Electron Microscopy

AbstractMorphological changes occurring in naturally weathered micas in seven residual soils from Ontario were studied. Splitting, exfoliation of the (100) planes, surface coats, filling of spaces with soil material as well as cracking and crumbling of (001) surfaces were the main morphological changes found to be taking place during natural weathering of mica particles. The significance of the observed feature in relation to the general theory of mica weathering is discussed.

AGE AND URANIUM CONTENT OF SOIL MICAS FROM ANTARCTICA BY THE FISSION PARTICLE TRACK REPLICA METHOD

A replica method was developed for fission particle track age dating and determination of uranium content of micas in a Wright Valley, Antarctica, soil and parent rock. The mica particles in the soil were relatively small, fragile, and easily dissolved by chemical etchings. Muscovite mica flakes were therefore used as a replicating substrate to register induced fission tracks of the soil mica. The micas from three soil horizons (0–10, 10–30, and 30–50 cm depths) and parent rock, in four size fractions (100–500,2–5, 0.2–2, and < 0.2μm) were examined to illustrate use of the method. The fission track age of the soil mica particles was 4.1±0.2 million years (MY), slightly older than the minimum landscape (glacial bench) age of 3.7 ± 0.2 MY obtained previously by K-Ar dating of a volcanic cone formed after the glacial valley was formed. The ages of the 2–5,0.2–2, and < 0.2μm fractions were the same as for the 100–500 μm flakes, when the spontaneous track density was calculated from that of the latter, in proportion to the U content. The fission track age of parent rock mica was 151 million years. The U content of the soil mica was 0.5 to 1.6 ppm which is 20 to 50 times higher than that of mica from the parent rock (0.03 ppm). The mica in the soil appears from age and petrographie thin-section results to be of pedogenic origin, formed by replacement in feldspars after the bench was carved. The fission particle track replica method is useful for age-dating of micas in soils, for determining trace amounts of uranium in micas, and for study of soil genesis in the Antarctic cold desert.

Mica Genesis in Hawaiian Soils

AbstractA soil mica having a formula Na0.11 NH40.06 K1–24 (Al, Si) (Al, Fe, Mg) O20 (OH)4 has been identified in soils of the wet uplands in the Hawaiian Islands. It contains 7.2% potash and is predominantly a mixer‐layered mica with vermiculite‐montmorillonite and chlorite. The mica is concentrated in the surface horizons, and its concentration increases with soils formed under increasing rainfall and elevation. Biological recycling of potash is proposed as a mechanism for its formation.

Weathering of Sodium‐Potassium Mica in Soils of the Virginia Piedmont

AbstractThe occurrence of paragonite, the Na‐analogue of muscovite, in intimate association with muscovite was observed in two soils and their parent materials in the Virginia Piedmont. A relatively constant Na/K molar ratio of approximately 1 was maintained in both the parent rocks and soils. This indicated that equal molar quantities of paragonite and muscovite were present and that the weathering rates of the two micas were similar.Vermiculite and kaolinite were the weathering products formed upon weathering of the mixed Na‐K mica. The vermiculite had the same expansion and contraction characteristics as that formed from a predominantly K‐mica. Consequently, the kind of weathering of muscovite and paragonite also appears to be similar.Paragonite is believed to be of more widespread occurrence than previous work has indicated. Its possible influence on soil genesis, morphology, and classification may be significant.

Negative Charge of Dioctahedral Micas as Related to Weathering

AbstractNegative charge and related characteristics of dioctahedral micas have been investigated by conducting artificial weathering studies on a muscovite from Ontario, Canada, and saprolitic micas from Virginia. Emphasis is given to the relationship between loss of potassium, increase in net negative charge, or cation exchange capacity, and expansion characteristics.Boiling solutions of acetic acid, sodium chloride and magnesium chloride removed potassium and sodium from a saprolitic mica but produced a negligible increase in cation exchange capacity. Expansion of the mica structure occurred following treatment with salt solutions but not with acid solutions. Boiling solutions of sodium citrate removed potassium effectively, produced marked expansion, and caused a large increase in cation exchange capacity. The small increase in cation exchange capacity resulting from acid and salt treatments is attributed to the hydrolysis of exchangeable aluminum to form hydroxy-aluminum polymeric groups, which can occupy exchange sites but remain non-exchangeable. The results of the sodium citrate tratement are attributed to the complexing of aluminum by citrate, thus releasing the hydroxy-aluminum polymeric groups from exchange positions and permitting an increase in cation exchange capacity.Molten lithium nitrate treatment of specimen muscovite produced a greater increase in cation exchange capacity than in the case of muscovite separated from soil-forming mica phyllite. The observed difference in charge characteristics, concomitant with the greater expansion of the muscovite, suggest that soil micas and specimen-type micas differ in their alteration tendencies.When interlayer hydroxy groups are eliminated and account is taken of residual sodium, potassium, and water, dioctahedral micas apparently lose no negative charge on expansion to vermiculite-like minerals.

Chloritized Weathering Products of a New England Glacial Till

AbstractThe clay mineralogy of a soil profile developed in a New England glacial till has been studied to a depth of 55 in. Degraded soil micas, probably produced by weathering, have been chloritized by both iron and aluminum hydroxide complexes. Aluminum and iron determinations and X-ray analyses indicate that iron chloritization has played the greater role. Citrate-extractable chlorite exists to a depth of 55 in. X-ray and heat stability data indicate that the chlorite is better developed or crystallized near the surface. X-ray and glycol retention data suggest that intense weathering at the surface has reduced the surface charge density of some of the degraded mica.