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Kaolin Deposits of Charentes Basin, France are clay deposits formed sedimentarily and then confined by other geological structures. ==Overview== The geological unit called Charentes basin is composed of Eocene and Oligocene deposits, laid above karstic limestone formations of the Campagnien, in the North of the Aquitaine Basin. The kaolin clays of Charentes belong to this mainly continental formation often referred as ''siderolithic'', of which the principal outcrop is situated in the South of the Charente Maritime department, going north-east from Bordeaux city. The quarries are scattered along a long, wide, north - south band. The clay concentrations of economic value are composed of a succession of clays, sands and pebbles. This torrential-stream deposit, close to enlaced rivers, laid to the deposition of sandy-clayey materials, with a variable iron content, coming from a lateritic weathering, of the French “Massif Central” granites.〔Kulbicki, 1956〕〔Marchadour, 1980〕〔Dubreuilh et Patel, 1982〕 The presence of numerous lignite rich levels indicates that the deposit was performed in the presence of abundant organic matter, leading to important pedogenetic and diagenetic possibilities of evolutions. These chemical and mineralogical evolutions (dissolution–crystallization) allow the neo-formation of kaolin and gibbsite, as well as iron sulfide.〔Delineau, 1994〕 At their basement, highly enlaced and with channel shapes, those deposits often fill karstic depressions, leading to the formation of ''clay wells''. The juxtaposition of features are sometimes without explanations using the deposition laws, probably in relation with post-sedimentary strain phenomena, eventually linked to substratum collapse.〔Delineau, 1994〕 In the upper part of the series, the deposits are more regular, with lateral extensions up to several hundreds of meters. Those complex geometries, with structures smaller than 20 meters, lead to particularly difficult recognition, estimation and exploitation phases. To this complex geometry, one should notice important lithology variations. The AGS company uses no less than 24 description codes and 8 colour codes, for its samples description. Those classes are subdivided to take into account the grade in organic matter, iron, titanium, potassium, the colour, and the aptitude to flow. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Kaolin Deposits of Charentes Basin, France」の詳細全文を読む スポンサード リンク
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