Influence of presence of ammonium in the hydrothermal illitization of smectite
Abstract
During diagenesis, several reactions induce changes both in phyllosilicates and organic matter, which in basins associated to the production of hydrocarbons leads to ammonium fixation in illite and micas [1] and to dissolution induced by organic acids [2] [3]. Dissolution processes may contribute to the smectite-to-illite transformation, stabilized by fixation of K (and NH4 +). Ammonium is a weak acid in solution. Under neutral conditions where the concentration of hydronium is very low (<10-7 M), ammonium contributes to smectite dissolution. The effect of organic acid on silicates dissolution is partially known, but the potential role of ammonium is completely novel.
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Scientific Research Abstracts Vol. 7, p. 79, 2017 ISSN 2464-9147 (Online) XVI International Clay Conference | ICC 2017 | Granada, Spain © Author(s) 2017. CC Attribution 3.0 License INFLUENCE OF PRESENCE OF AMMONIUM IN THE HYDROTHERMAL ILLITIZATION OF SMECTITE maría bentabol (1)*, daniel lamarCa-irisarri (2), eduardo flores (2), f. javier Huertas (2) (1) Department of Inorganic Chemistry, Crystallography and Mineralogy. University of Málaga. Campus de Teatinos s/n, 29071, Málaga, Spain, (2) Instituto Andaluz de Ciencias de la Tierra-IACT (CSIC-University of Granada). Avda. de las Palmeras 4, 18100 Armilla, Granada, Spain During diagenesis, several reactions induce changes both in phyllosilicates and organic matter, which in basins associated to the production of hydrocarbons leads to ammonium fixation in illite and micas [1] and to dissolution induced by organic acids [2] [3]. Dissolution processes may contribute to the smectite-to-illite transformation, stabilized by fixation of K (and NH4 +). Ammonium is a weak acid in solution. Under neutral conditions where the concentration of hydronium is very low (<10-7 M), ammonium contributes to smectite dissolution. The effect of organic acid on silicates dissolution is partially known, but the potential role of ammonium is completely novel. In order to study the possible influence of NH4 + in the smectite-to-illite transformation reaction, a series of hydrothermal experiments were carried out at 100, 150 and 200 ºC, for 15 to 90 reaction days and two NH4 + concentrations (0.1 and 0.01 M). Solids were characterized after alteration by XRD and FTIR. The results show that in these conditions, the smectite incorporates NH4 + in the structure, and smectite dissolution is corroborated by the formation of Kand NH4 +-zeolites, at pH basic, and of K-feldspars and buddingtonite. Nevertheless, the XRD patterns reveal that, in addition these phases, the solid products include a small peak at ~10 A, suggesting formation of illite Thus, presence of NH4 + seems to promote smectite-to-illite transformation reaction through the mechanism: NH4 +- smectite → interstratified I/S → illite. Acknowledgments: financial support was obtained from MINECO (CGL2011-22567, CGL2014-55108P), with contribution of FEDER funds. [1] Williams L.B., Ferrell R.E. (1991). Ammonium substitutions in illite during maturation of organic matter. Clays and Clay Minerals 39, 400-408. [2] Ramos E., García-Palma S., Rozalen M., Johnston C.T., Huertas F.J. (2014). Kinetics of montmorillonite dissolution. An experimental study of the effect of oxalate. Chemical Geology 363, 283-292. [3] Ramos M.E., Cappelli C., Rozalén M., Fiore S., Huertas F.J. (2011). Effect of lactate, glycine, and citrate on the kinetics of montmorillonite dissolution. American Mineralogist 96, 768-780.