ISSN:0044-3263    

DOI:10.1002/jpln.19761390102

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

ISSN:0044-3263    

DOI:10.1002/jpln.19761390103

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

The transformation of mica‐like layer silicates to expansible three‐layer day mineralsFirst of all a preliminary survey is given of those authors who have so far carried out investigations on certain minerals about transformations of layer‐silicates to expansible three‐layer clay minerals.It can be deduced from these investigations that the most important presupposition for a transformation, is the setting free of potassium and the reduction of the layer‐charge.The knowledge of the presuppositions of a transformation was achieved mainly in model tests (deposit‐clays), which also explain the running off of the exchanges of the intermediate layers. To demonstrate transformation processes with natural clay fractions of soils, requires an extensive clay fractionizing which is accomplished by means of centrifuges.Personal investigations with fractionized clays of a Chernozem have shown, that in soils, the transformation of illite into expansible three‐layer‐minerals occurs at the same time as the decrease in size of grain. Although the illites which are in the process of transformation reach an expansion up to 18 A from about 0,2 μ granular size, a qualitative difference exists (layer‐charge, contraction tendency) to the genuine montmorillonites, that only becomes less at the finest fractions>0,01 μ.The investigations with other soils (‘gray brown‐soils’,‘acidic brown soil’) however, reveal that there is no suitable transformation scheme for all soils. Depending on the milieu in which the soil development has taken place, characteristic transformation sequences result. Because of the hitherto existing results three development‐models were introduced and discussed, each of whic

ISSN:0044-3263    

DOI:10.1002/jpln.19761390104

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

The Weathering of Mafic Chlorites in Soils (A Review)Recent results from the literature and some own data on chlorite weathering as derived from soil profile studies and laboratory work on artificial weathering are summarized. Among the two possible pathways of chlorite weathering ‐ vermiculitization after removing the hydroxide layer and complete dissolution ‐ vermiculitization appears to occur in rather “closed” systems not too acid and poor in organic compounds (e.g. saprolites). Complete dissolution, on the other hand, prevails in strong acid parts of the solum rich in organic matter, e.g. in podzol A horizons. Due to the presence of micaceous minerals in most profiles which also serve as a source for expandable mixed layer species the exact pathway of the chlorite during weathering cannot be followed up

ISSN:0044-3263    

DOI:10.1002/jpln.19761390105

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

Weathering of feldspars and their importance for the formation of clay mineralsIn quaternary sediments weathering and transformation of layer silicates, and in particular of biotites play a dominant role in the formation of clay minerals in soils of the moderately (semi) humid climate. In contrast, conflicting results were published concerning the participation of feldspar weathering for pedogenetic clay mineral formation. Another question is, whether formation of clay minerals in the fractions 0,6–0,2 μ m and<0,2μ m by chemical weathering of micas and feldspars is the dominating process, or the formation of „pseudo clay minerals”︁ in the fraction 2–0,6 μ m by cryoclastic desintegration of micas and feldspars, as proposed by several authors. It is not yet clear, which clay minerals are formed from the weathering products of feldspars. — A necessary condition for a conclusive study of these problems is the vertical sedimentary homogeneity of the soil forming material.In eight loess soils investigated of very different genesis (a syrosem, chernozems, brown forest soils and a „braunlehm”︁) there were no indications for clay formation in the coarse clay fraction (2–0,6μm) by physical weathering of feldspars. This was also true for the loess‐syrosem of young Würm age, where the former climatic conditions should have promoted this process.In the chernozems, the brown forest soils and the braunlehm the proportion of illite and Smectite newly formed were about 25–40% and 45–50% respectively. They are derived mainly from layer silicates but also from feldspars. In the chernozems 15–20%, the recent brown forest soils 20–25%, in a brown forest soil from the last interglacial period more than 30% and in the braunlehm of middle pleistocene age more than 40% of the original feldspars were destroyed by chemical weathering and had participated in clay formation, especi

ISSN:0044-3263    

DOI:10.1002/jpln.19761390106

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

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 duri

ISSN:0044-3263    

DOI:10.1002/jpln.19761390107

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

Formation and properties of amorphous clay constituents in soils of the temperate‐humid climate regionA review of literature and of some own work was given on formation and properties of amorphous clay constituents which occur along with crystalline clay minerals in soils. By that the importance of soil amorphous material with respect to pedologic‐agricultural and social‐environmental problems was tried to emphasize.At the beginning some clarification of the different terms used for inorganic amorphous clay constituents and a sort of difinition of the different kinds of amorphous materials seemed to be evident. Then, the occurence and the formation of amorphous material in soils of the temperate‐humid climate region was commentated. As a result of this it was stated that amorphous clay constituents occur mainly as coatings on negatively charged surfaces of crystalline layer silicates. From the grouping of amorphous substances around negatively charged cores (layer silicates or AlIV‐cores in allophanic soils, respectively) it was deduced that the organisation of amorphous clay constituents and allophanes as well as synthetic aluminosilicates might be due to an unique structural principle, which was tried to explain more detailed.The methods used for determination of amorphous materials, especially allophanes, were discussed. Since the determination of amorphous clay constituents by chemical dissolution techniques is ambiguous with respect to soils containing different weathering stages of crystalline layer silicates as well, some suggestions were made for characterizing amorphous substances in soils by cation exchange and anion adsorption properties. Finally the importance of exchange‐reactions caused by specific adsorption of ions and molecules (e.g. nutrients and pesticides) was indicated. Furthermore, the possibility was mentioned that harmful environmental substances might be bound (neutralized) and waste nutrients might be recycled by specific adsorption on amorphous soil c

ISSN:0044-3263    

DOI:10.1002/jpln.19761390108

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

Content, Transformation and Neoformation of Clay Minerals in near shore Sediments of the North SeaFrom literature and our own results, approximate quantitative values are given on the mineral content of clay and silt fractions of marine sediments from the Wadden Sea. Besides this, the extent of clay mineral transformation and neoformation in a marine environment is discussed.According to our knowledge, the extent of clay mineral transformation and neoformation must be unimportant because the sea water and pore solution of the sediments seems to be ‐ with the exception of a small Mg‐surplus — something like anequilibrium solutionfor three‐and fourlayer minerals, which neither favors a considerable base fixation nor base release. Therefore illite neoformation during halmyrolysis or early diagenesis seems to be impossible because of unfavourable relations of potassium to all other cations in the sea water. Obviously the neoformation of illite is connected with later diagenesis. The processes of clay mineral neoformation in a marine evironment are probably restricted to the formation of amorphous (Mg‐) Fe‐Si‐particles, which may be first steps in the formation of chamosites, chlorites

ISSN:0044-3263    

DOI:10.1002/jpln.19761390109

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

Genesis of Secondary Al‐(Fe‐)ChloritesComparing the results of soil investigations with those obtained from laboratory syntheses it was concluded that secondary Al‐Fe‐chlorites in soils of moderate cool‐warm‐humid climates mainly develop through protonisation of Al and Fe in the mineral structure of expanded dioctahedral vermiculites with subsequent hydrolysis in the interlayer space. In this process characteristics of the mineral itself (e.g. layer charge) as well as carbonic acid and soil organic acids (as proton suppliers) are the most important factors.From this, the further conclusion was drawn that in the pH‐range 6, 5–6 secondary chlorites begin to develop increasingly until pH5 (development conditions) and in the pH‐range 5–4,5“conservation conditions” exist. ‐ At pH<4,5 secondary chlorites are unstable (dissolution conditions) through protonisation of Al‐Fe‐hydroxy polymers (reverse of hydrolysis) with subsequent solubilization and leaching especially through complexation by soil organic acids. ‐ As remaining minerals in this weathering sequence smectites occur, resulting from the decrease of layer charge in vermiculites through the chloritization process, thus indicating that chloritization may be an important process for the genesis of smectites u

ISSN:0044-3263    

DOI:10.1002/jpln.19761390110

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

ISSN:0044-3263    

DOI:10.1002/jpln.19761390111

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY