Mg-Rich smectite "precursor" phase in the Tagus basin, Spain



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Santiago Buey, Cristina de and Súarez Barrios, Mercedes and García Romero, Emilia and Doval, Mercedes (2000) Mg-Rich smectite "precursor" phase in the Tagus basin, Spain. Clays and clay minerals, 48 (3). pp. 366-373. ISSN 0009-8604

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The pink clays from the Tagus basin, Spain, were characterized by X-ray difraction (XRD),
infrared spectroscopy (IR), scanning electron microscopy (SEM), and transmission electron microscopy
(TEM). Chemical data were obtained by plasma emission spectroscopy and analytical electron microscopy
(AEM), and specific surface and cation-exchange capacity were measured also. The data indicate that
these pink clays are primarily stevensite. This Mg-rich smectite is characterized by poor crystallinity, a
high degree of structural disorder, trioctahedral character (pure magnesian), a very low cation-exchange
capacity, a very small crystal size (which generates an abnormally high specific surface area), and a
deficiency of octahedral cations. On the basis of the very small crystal size, a large number of edge
dislocations, the lack of periodicity (turbostratic) in the structure, and a cellular (spherical) texture observed
by TEM, we consider this occurrence to be an early stage of crystallization. Unlike other precursor
clay materials described in the literature, this clay is not an alteration of volcanic ash, but it was generated
by precipitation from a Si- and Mg-saturated medium.

Item Type:Article
Uncontrolled Keywords:Precursor Clay, Smectite, Stevensite, Tagus Basin (Spain), Incipient Crystallization
Subjects:Sciences > Geology > Mineralogy
ID Code:13394
Deposited On:13 Oct 2011 10:11
Last Modified:11 Dec 2018 08:47

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