Mineralogical and clay mineralogical aspects of loess research

Tonmineraleigenschaften und -umwandlungen in parabraunerde-profilpaaren unter acker und wald in Süddeutschland

Changes of three-layer clay minerals by native K in holocene loess derived soils of Central Germany and Lower Bavaria.



Transformations of the clay minerals illite, vermiculite and smectite were determined in Central German (31 profiles) and Lower Bavarian loess districts (5 profiles) using 31–36 soil properties. To get significant differences between solum and sediment, the multivariate diskriminant analysis was applied.



In the Central German loess district the following properties were crucial, to receive significant separation between solum-horizons and sediments: smectite content, several values of potassium fixation, interlattice potassium. Important were also some parameter of the K-Ca-exchange curve: Activity ratio of a soil solution in equilibrium with a soil (ARo), buffering capacity of the soil for K at equilibrium (BCKE), labile K(K1), exchange capacity of the exchange sites with a specific affinity for K minus labile K(ECx—K1). The differences of these values can be explained by assuming that (at pH 6–7) the beidellitic layers of smectites of the parent loess were transformed to illitic layers in the solum-horizons.



In the Lower Bavarian loess landscape potassium fixation, total K in clay fraction (< 2 μm) and the parameters of the K-Ca-exchange curve indicate the same clay mineral transformation as in Central Germany. Smectite values were not introduced to the diskriminant function, because they were highly significantly correlated with potassium fixation. In this case potassium fixation has caused a better separation between the solum-horizons and the parent loess than X-ray data.



From these results, from total -K of the fraction 2–20μm (solum-horizons smaller than sediments) and the vermiculite content fo the clay fraction, it can be concluded, that the rate of potassium release from micas and the rate of potassium fixation by beidellitic sheets during the Holocene period were nearly equal.

Veränderungen von Dreischicht‐Tonmineralen durch natives K in holozänen Lößböden Mitteldeutschlands und Niederbayerns

Interlayer K from two biotites of different origin was extracted with octadecylammonium chloride (ODA) and sodium chloride/sodium tetraphenylboron (STB) before and after oxidation with saturated bromine water (Br 2 ). Potassium release, Fe oxidation and Fe ejection from octahedra were measured. With ODA and STB the untreated biotites released between 40 and 90% of initial interlayer K, the muscovite less than 5%. After Br 2 treatment, substantially less K was extracted from both biotites. Suppression of K release was caused by the formation of octahedral vacancies formerly occupied by Fe. The extent of Fe ejection was not proportional to the extent of octahedral Fe oxidation. During Br 2 treatment, the biotites transformed into hydrobiotite. The hydrobiotite sample, high in Fe ejection during preceding Br 2 treatment, strongly resisted subsequent K extraction with STB, whereas the sample with minor Fe ejection transformed to vermiculite. Octadecylammonium chloride extracts K more effectively than STB from biotites intermediate between trioctahedral and dioctahedral structure and is considered to be suitable for the distinction between biotite K and muscovite K

Potassium release from micas and characterization of the alteration products

Fur Acker-Wald-Vergleichspaare von Parabraunerden aus jungpleistozanem Los im Gebiet sudlich von Wurzburg wurden Bilanzen der Veranderung und Verangerung von Tonfraktionen, Tonmineralen und im Ton silikatisch gebundenem Kalium, Magnesium und Eisen gerechnet.



Die Tonbildung liegt bei 63–98 kg/m2, wobei auf die Fraktion <0, 1 μn etwa 60–80% entfallen. Die Tonverlagerung schwankt zwischen 35 und 51 kg/m2, woran die Fraktionen <0,2 μm in gleicher Weise, der Grobton in geringerem Ausmas beteiligt sind.



Bei der holozanen Bodenbildung werden im Ton <2 μm durchschnittlich 121 kg Illit/m2, 16 kg Vermiculit/ m2 und 11 kg Kaolinit/ gebildet. Dem steht ein Smectitverlust von ca. 68 kg/m2 gegenuber. Die grosten Veranderungen der Tonmineralmengen treten in der Fraktion <0, 1 μm auf, die eine Smectit-Illitumwandlung erkennen lassen. Mit 23 kg/m2 ist Illit zur Halfte an der Tonverlagerung beteiligt, gefolgt von Smectit und Vermiculit mit je 9 kg/m2 und Kaolinit mit 5 kg/m2. Der Vergleich der verlagerten mit den vorhandenen Mengen last jedoch keine Bevorzugung bestimmter Tonminerale bei der Verlagerung erkennen.



Im Ton dominieren die Gewinne von silikatisch gebundenem Eisen (3, 07–4, 32 kg/m2) und Kalium (2, 75–3, 84 kg/m2) gegenuber Mg (0, 57–1, 15 kg/m2). Die drei Elemente reichern sich am starksten im Feinton an. Die bei den Gewinnen genannte Reihenfolge bleibt bei der Elementverlagerung erhalten. Die Bilanzen der silikatisch gebundenen Elemente werden im Zusammenhang mit der pedogenen Illitbildung sowie Biotitverwitterung und Vermiculitzerkleinerung diskutiert.



Balances of alteration and migration of clay fractions and clay minerals in Gray Brown Podzolic Soils from Loess



Balances of alteration and migration of clay fractions, clay minerals, K, Mg and Fe bound in clay silicates were calculated for Gray Brown Podzolic Soils (Parabraunerden) derived from Young Pleistocene Loess below arable and forest land in the district south of Wurzburg.



The extent of clay formation lies between 63 and 98 kg/m2, of which 60–80 % belong to the fraction <0.1 μm. The clay migration varies between 35 and 51 kg/m2, the fractions < 0.2 μm (especially the fraction <0.1 μm) predominating, the coarse clay being involved only to a smaller extent.



During Holocene soil formation 121 kg illite, 16 kg vermiculite and 11 kg kaolinite per m2 are formed in the clay fraction (< 2 pm). The loss of smectite amounts to 68 kg/m2. The biggest alterations of the clay mineral quantities occur in the fraction <0.1 pm; they indicate a smectite-illite transformation. Illite, at 23 kg/m2, accounts for half of the clay migration, followed by smectite and vermiculite each at 9 kg/m2 and kaolinite at 5 kg/m2. When comparing the migrated with the present amounts no preference of certain clay minerals during clay migration can be determined.



In the clay fractions the gained Fe (3.07−4.32 kg/m2) and K (2.75−3.84 kg/m2) predominate over Mg (0.57−1.15 kg/m2). The three elements accumulate to the greatest extent in the fine clay fraction. The element migration parallels the gain. The balances of the elements are discussed in connection with pedogenic illite formation as well as biotite and vermiculite disintegration.

Bilanzierung der Tonbildung und ‐verlagerung sowie der Tonmineralumwandlung in Löß‐Parabraunerden

Transformation of three-layer silicates through K-release and K-uptake (A review).



In soils formed from unconsilidated sediments with illite-vermiculite-smectite mixtures in their clay fractions the clay mineral transformation from illite to vermiculite and smectite between pH 5 and 7 cannot be considered so far as proven on the grounds of available analytical data. Studies of soil profiles showed that the formation of illite from expandable three layer silicates predominates over the formation of smectite from illite. Practically all samples of loess and calcareous tills of the areas discussed contain smectites. K loesses between pH 5 and 7 are probably very small, because K released during the formation of vermiculites from micas is immediately fixed by smectitic layers which are converted to illite. In those soils potential K fixation of the clay fraction (« 2 μ) is lower than in the corresponding parent sediments despite of vermiculite formation in the soils. Further analytical data (X-ray, interlattice-K, K-selectivity, specific surface) support the hypothesis of illitization of smectites during soil formation.

Umwandlungen von Dreischichtsilikaten unter K‐Abgabe und K‐Aufnahme

Die Pelosole und Pseudogleye aus den Sedimenten Amaltheenton (Lias δ), Posidonienschiefer (Lias α) und Opalinuston (Dogger ae) im Vorland der Frankenalb wurden mit Hilfe von 16 Eigenschaften getrennt, namlich mit sieben Kornungsdaten und neun chemischen Daten, die tonmineralspezifische Eigenschaften darstellen. Bei den Versuchen, mit Hilfe der multivariaten Diskriminanzanalyse die Sedimente untereinander und das Solum von den Sedimenten zu trennen, waren acht Eigenschaften fur die Unterscheidung des Gesamtprobenmaterials in verschiedene Gruppen wichtig. Eigenschaften mit groser Trennqualitat waren die effektiven Pufferkapazitaten fur K (BCKe in mval/100 g Boden und 100 g Ton/M1/2), die K-Fixierung (mg K/100 g Boden und 100 g Ton) und das labile Kalium (mval K/100 g Boden). Das mobile K (ARo in M1/2) war bei allen Trennungen wie Solum von Sediment, Solum von Solum und Sediment von Sediment bedeutsam. Die Pseudogleye wurden am signifikantesten von den Sedimenten Amaltheenton und Opalinuston getrennt. Auserdem konnten die Pelosole sehr gut von den Sedimenten Amaltheenton und Opalinuston einerseits und Posidonienschiefer andererseits getrennt werden. Die statistisch gesicherte Zunahme der BCKe und die Abnahme von ARo geben ebenso wie einige Rontgenbeugungsdiagramme zu erkennen, das in den Pseudogleyen aus Amaltheen- und Opalinuston und den Pelosolen aus Posidonienschiefer aufweitbare Formen von 2:1-Mineralen entstanden sind.



Distinctions of Clay Properties in Claystone of the Franconian Lias-and Doggerlandscape and Their Soils



Pelosols and Pseudogleys derived from the sediments of the Amaltheen Clay (lias δ), Posidonia Shale (lias δ) and Opalinus Clay (dogger ae) formations in the forelands of the Alb Mountains in Franconia were separated using 16 properties (seven textural and nine chemical properties, the latter of which indicate clay specific properties).



Multivariate discriminant analysis was able to distinguish sediments from sediments, sediments from soils and soils from soils. Eight properties were important for discriminating the samples into several groups. Properties with the greatest discriminating quality were the effective buffering capacity for K (BCKe in mval/100 g soil and 100 g clay/M1/2), the K-fixation (mg K/100 g soil and clay), and the labile K (mval K/100 g soil). The mobile K (ARo in M1/2) was also an important property. The Pseudogleys were most significantly separated from the Amaltheen Clay and Opalinus Clay sediments. Furthermore, the Pelosols could be significantly separated from Amaltheen Clay and Opalinus Clay on one side and Posidonia Shale on the other. The statistically significant increase of the BCKe and the decrease of ARo as well as some X-ray diagrams suggest that in Pseudogleys derived from Amaltheen Clay and Opalinus Clay and in Pelosols derived from Posidonia Shale expandable forms of 2 : 1 minerals were formed from 10 A-minerals.

Unterschiede von Toneigenschaften in Tonstein der fränkischen Lias- und Doggerlandschaften und ihren Böden†

An Kornfraktionen von Parabraunerden aus Los und Pelosolen aus Gipskeuper-Tonmergeln wurden das durch Octadecylammonium-chlorid (ODA) extrahierbare Kalium und das Zwischenschicht-Kalium (Kzw) durch thermische Dissoziation von sorbiertem NH4 bestimmt. Die Extraktion mit ODA ist ein diffusionskontrollierter K-Austausch. Dies geht aus dem Anstieg der K-Freisetzung-bei kleiner Einwaage und geringer K-Konzentration hervor. Die Vorrate an ODA-Kalium (= Biotit-K) waren in den Tonmergel-Pelosolen deutlich hoher als in einer Los-Parabraunerde (30 und 34 t vs. 22 t/ha, jeweils 55 cm Bodentiefe). Das Maximum der Freisetzung von ODA-Kalium wurde bei beiden Boden-formen in der Fraktion 2–6 μm gemessen. Die Anteile des Kzw am Kt lagen umso hoher, je kleiner die Korngrose war und erreichten in der Fraktion < 2 μm zwischen 70 und 80%. Rontgenbeugungsdaten geben Hinweise auf unterschiedliche Mineralgenesen in beiden Sedimenten, dies wird durch die Kzw-Werte in den verschiedenen Fraktionen gestutzt.



Das selektiv freisetzbare Zwischenschichtkalium ist an den keilformig aufgeweiteten Schichten von Illiten gebunden und last sich von der Hauptmenge des Zwischenschicht-Kaliums durch leichtere Extrahierbarkeit bei den ersten 3 bis 5 Gluhbehandlungen unterscheiden. Dies sind im Mittel 22% des gesamten Zwischenschicht-Kaliums im Ton.



The determination of preferentially releasable potassium in hapludalf from loess and chromudert from gipskeuper clay marl



Octadecylammonium-chloride (ODA)-extractable potassium and interlayer potassium (KZW), exchanged after thermal dissociation of adsorbed NH4, were determined on particle size fractions of soils from gipskeuper clay marl (typic chromudert) and loess sediments (shallow hapludalf). The extraction by ODA is a diffusion controlled K-exchange process. This is shown by the increase of K-release at small sample quantity and K-concentration in the extraction solution. The ODA-potassium supplies (= Biotit-K) of the two typic chromudert were significantly higher than that of the shallow hapludalf (34000 and 30000 kg/ha vs. 22000 kg/ha, to a depth of 55 cm). Biotit-K was highest in the 2-6μm-fraction for both soils. The smaller the particle size, the larger were the amounts of KZW In the clay fractions of all samples they reached between 70 and 80% of total K (Kt). XRD-data give evidence of different mineral genesis processes between the two types of sediments. This is supported by the KZW-values of the particle-size fractions.



The selectively releaseable interlayer potassium is associated with wedge shaped layers of illite. It can be differentiated from the bulk interlayer potassium by its preferential extractability in the first 3 to 5 heating treatments. This potassium quantity is, on an average, 22% of total clay interlayer potassium.

Ernst-A. Niederbudde

Papers

Umwandlungen von Dreischichtsilikaten unter K‐Abgabe und K‐Aufnahme

Unterschiede von Toneigenschaften in Tonstein der fränkischen Lias- und Doggerlandschaften und ihren Böden†

Die Bestimmung von selektiv freisetzbarem Kalium in Parabraunerde aus Löß und Pelosol aus Gipskeuper-Tonmergeln†