Petrography and application of the rietveld method to the quantitative analysis of phases of natural clinker generated by coal spontaneous combustion

• Published in: Earth sciences research journal 2010-06, Vol.14 (1), p.17-30
• Main Authors: Henao M., Jose Antonio, Carreno P., Angelica Maria, Quintero D., John Alexander, Candela H., Sol Angel, Rios R., Carlos Alberto, Ramos G., Miguel A, Pinilla A., Jesus Andelfo
• Format: Article
• Language: English
• Subjects: Combustion; Crystals; Diffraction; GEOSCIENCES, MULTIDISCIPLINARY; Methods; Structure; X-rays
• ISSN: 1794-6190; 2339-3459

Fine-grained and mainly reddish color, compact and slightly breccious and vesicular pyrometamorphic rocks (natural clinker) are associated to the spontaneous combustion of coal seams of the Cerrejon Formation exploited by Carbones del Cerrejon Limited in La Guajira Peninsula (Caribbean Region of Colombia). These rocks constitute remaining inorganic materials derived from claystones, mudstones and sandstones originally associated with the coal and are essentially a complex mixture of various amorphous and crystalline inorganic constituents. In this paper, a petrographic characterization of natural clinker, as well as the application of the X-ray diffraction (Rietveld method) by mean of quantitative analysis of its mineral phases were carried out. The RIQAS program was used for the refinement of X ray powder diffraction profiles, analyzing the importance of using the correct isostructural models for each of the existing phases, which were obtained from the Inorganic Crystal Structure Database (ICSD). The results obtained in this investigation show that the Rietveld method can be used as a powerful tool in the quantitative analysis of phases in polycrystalline samples, which has been a traditional problem in geology. Key words: Rietveld method, Cerrejon, X-ray powder diffraction, natural clinker. Rocas pirometamorficas (clinker natural) de grano fino y coloracion principalmente rojiza, compactas, y ligeramente brechadas a vesiculares estan asociadas a la combustion espontanea de mantos de carbon de la Formacion Cerrejon explotados por Carbones del Cerrejon Limited en la peninsula de La Guajira (Region Caribe de Colombia). Estas rocas constituyen materiales inorganicos remanentes derivados de arcillolitas, limolitas y areniscas originalmente asociadas con carbon y son esencialmente una mezcla compleja de diferentes constituyentes inorganicos amorfos y cristalinos. En el presente trabajo, se llevo a cabo la caracterizacion petrografica del clinker natural, asi como la aplicacion de la difraccion de rayos-X de polvo (metodo de Rietveld) para el analisis cuantitativo de las fases minerales presentes de las rocas en estudio. El programa RIQAS fue utilizado para el refinamiento de perfiles de difraccion de rayos-X de polvo, analizando la importancia de utilizar los modelos isoestructurales adecuados para cada una de las fases presentes, los cuales se obtuvieron de la base de datos Inorganic Crystal Structure Database (ICSD). Los resultados obtenidos en la presente