Formation Of Phyllosilicates Research Articles

Chemical composition of clay minerals and shales of Anatolian Tertiary sediments: A global interpretation

Contrary to an earlier proposal, an increase in the Ca/Mg ratio of shaly sediments with geological age is not of a general validity, although it may be true for cratonic areas. In deeply fractured belts, such as those of Anatolia, Mg is supplied to the sedimentary media via detritic minerals and aqueous solutions by main magmatic as well as hydrothermal phases. Thus, in suture belt regions, Mg seems to be dominant over Al, and contribute to the formation of phyllosilicates and carbonates. For such formations of Anatolia, it is not possible to speak of a decrease in the Ca/Mg ratio with age from the Cambrian to the Neogene.

Formation of Phyllosilicates and Zeolites from Pure Silica-Alumina Gels

AbstractThe hydrothermal aging of pure silica—alumina gels in presence of 10 ml of 0.1 N sodium hydroxide solution at 175, 150 and 130°C for 8–30 days led to the synthesis of zeolites and the phyllosilicates, beidellite and kaolinite. The solution was neutralized by a partial hydrolysis of the gel which readily reorganized into a prezeolitic material. At pH values ⩾ 9, with 300 or 600 mg of gel, it evolved towards the crystalline zeolites P and S, with low surface area (7–100 m2/g) but high exchange capacity (300–475 m-equiv./100 g). With gel amounts of 600–2400 mg, and pH values of 8–5.5, the prezeolitic material provided rows of O—Si—O—Al—OH which recombined to form the phyllosilicate structures. Surface area increased (170–325 m2/g) but exchange capacity decreased (100–250m-equiv./100 g). The results obtained by various techniques (XRD, DTA, IR) indicated a moderate degree of crystallinity of these phyllosilicates; in addition, X-ray powder diffraction suggested that hk bands were the first to develop.The positive results obtained with a 0.40 ratio Al2O3 gel compared with the negative results obtained with 0.30 or 0.50 Al2O3 gels indicate that the gel composition is very important for the formation of phyllosilicates under the experimental conditions.