Mineralogical characterization of silica sinters from the El Tatio geothermal field, Chile

descriptionPublicationkeyboard_double_arrow_right Article 01 Aug 2008 English Publisher:Mineralogical Society of AmericaJournal:American Mineralogist, volume 93, pages 1,373-1,383 (issn: 0003-004X,

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Authors: García-Vallés, M.; Fernandez-Turiel, J. L.; Gimeno, D.; Saavedra Alonso, Julio; Martínez-Manent, S.;

doi: 10.2138/am.2008.2583

handle: 10261/31755

Mineralogical characterization of silica sinters from the El Tatio geothermal field, Chile

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Abstract

Silica sinters, deposited from alkali chloride waters in the El Tatio geothermal field in northern Chile (22°20'S, 68°01'W), have been characterized by XRD, SEM, TG-DTA, and FTIR. The dominant silica phase is opal-A. Minor contents of opal-A/-CT and opal-CT are also present together with halite (NaCl), sylvite (KCl), and realgar (AsS). Accessory phases include teruggite [Ca4MgAs2B12O22(OH)12·12(H2O)], sassolite (H3BO3), and detrital quartz (SiO2). FWHM values reflect the immature nature of the studied opal-A. DTA heating experiments of opal-A show cristobalite crystallization at ~1000 °C, whereas DTA cooling experiments show the β -alfacristobalite transformation at ~200 °C. The total weight loss is related to changes in the sinter microtextures, mineral phases, and organic matter contents. FTIR spectra show the effects of silica maturation as consequence of the loss of trapped and absorbed water attached to silanols.

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11 páginas.

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Keywords

FTIR, XRD, Opal-A/-CT, Opal-A, TG, Opal-CT, DTA

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