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3. Phyllosilicates in the sediment-forming processes: weathering, erosion, transportation, and deposition

Creator:
Jiří Konta
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, jílové minerály, zvětrávání, eroze (geologie), doprava, chemická stálost, krystalizace, clay minerals, weathering, erosion, transportation, chemical stability, crystallization, phyllosilicates, structural variability, sediment-form ing processes, rock-forming silicates, deposition, index of corrosion, volcanic glass, chemical microenvironment, clay pseudomorphs, capillary system, river suspensions, lutites, deflocculation, coagulation, fluvial, lacustrine and marine muds, 7, and 551
Language:
English
Description:
a1_Phyllosilicates are classified into the following groups: 1 - Neutral 1:1 structures: the kaolinite and serpentine group. 2 - Neutral 2:1 structures: the pyrophyllite and talc group. 3 - High-charge 2:1 structures, non-expansible in polar liquids: illite and the dioctahedral and trioctahedral micas, also brittle micas. 4 - Low- to medium-charge 2:1 structures, expansible phyllosilicates in polar liquids: smectites and vermiculites. 5 - Neutral 2:1:1 structures: chlorites. 6 - Neutral to weak-char ge ribbon structures, so-called pseudophyllosilicates or hormites: palygorskite and sepiolite (fibrous crystalline clay minerals ). 7 - Amorphous clay minerals. Order-disorder states, polymorphism, polytypism, and inters tratifications of phyllosilicates are influenced by several factors: 1) a chemical micromilieu acting during the crystallization in any environment, including the space of clay pseudomorphs after original rock-forming silicates or volcanic glasses; 2) the accepted thermal energy; 3) the permeability. The composition and properties of parent rocks and minerals in the weathering crusts, the elevation, and topography of source areas and climatic conditions control the in tensity of weathering, erosion, and there sulting assemblage of phyllosilicates to be transported after erosion. The enormously high accumulation of phyllosilicates in the sedimentary lithosphere is primarily conditioned by their high up to extremely high chemical stability in water-rich environments (expressed by index of corrosion, IKO). Clastic material eroded fro m weathering crusts and transported in rivers contains overwhelming amounts of phyllosilicates inherited from original rocks. In geological literature, the newly formed phyllosilicates crystallizing in weathering crusts including soils as dominating global source of argillaceous lutite accumulations in the sedimentary lithosphere have been overestimate for a long time., a2_The dissolution of silicates in different dense rocks under conditions of weathering and the crystallization of newly formed phyllosilicates has been strongly and for long periods influenced by chemical microenvironments within each clay pseudomorph. Coarser fragments of eroded argillaceous rocks and crystals of phyllosilicates from different bedrocks and soils are very sensitive to impacts and pressure from fragments of co-transported harder and denser rocks and minerals in turbulent fluvial and similar currents. This is the most important mechanical phenomenon supporting the enormous accumulation of lutite rocks rich in phyllosilicates in the sedimentary lithosphere. The summarized new observations and interpre tations are stressed in eleven key poin ts. Erosion and water transportation of detrital material are explained in the terms of hydration, softening, swelling, physical disintegration, grinding, milling, abrasion, delamination, dispersi on, and sorting. The deposition of phyllosilicates in different fluid dynamics of streams is expressed by Re and Fr numbers and explained as unflocculated and floccu lated suspensions. Phyllosilicates an d accompanying detrital minerals in recent marine muds covering vast areas of seas and oceans as well as in lacustrine muds correspond with those transpor ted in fluvial suspensions., Jiří Konta., and Obsahuje bibliografické odkazy
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