Abstract
AbstractThe numerous kaolin deposits located in Patagonia, Argentina, have been formed by hypogene or supergene processes. The primary origin has been established from O18 and D isotopic composition of the main minerals, kaolinite and/or dickite, and from the behaviour of certain elements during the alteration. The aim of this paper was to find if there is a tool, other than oxygen-deuterium data, to establish the origin of the Patagonian kaolin deposits. To handle the large number of variables per sample, a statistical multivariate study was used. The Principal Component method defines, on one hand the variables that better characterize each deposit and, on the other hand, the correlation between them. Fifty seven elements were considered and those that were not explained using these two components (which represent 75% of the total variance of the model) were discarded. As a result, the contents of Fe2O3, P2O5, LOI, Sr, Y, Zr, V, Pb, Hf, Rb, S and REE were used and the results show that the two components separate the deposits into two fields that are consistent with the process of formation. The first component indicates that Fe2O3, Y, Rb, U and HREE are more abundant in the supergene deposits, whereas, Sr, Pb, S and V are more abundant in the hypogene deposits. The second component shows that S, P2O5 and the LREE are enriched in the hydrothermal deposits, whereas Zr is more abundant in those formed under weathering conditions.
Highlights
The mobility of major, minor and rare-earth elements (REE) during alteration processes in different environments has been documented by numerous authors and has been used to discriminate the origin of kaolin deposits. (Sturchio et al, 1986; De Groot & Baker, 1992; Gouveia et al, 1993; van der Weijden & van der Weijden, 1995; Condie et al, 1995; Dill et al.,1997, 2000; Galan et al, 2007; Pandarinath et al, 2008, among others)
Only the contents of Fe2O3, P2O5, Sr, Y, Zr, V, Pb, Hf, Rb, S, REE and LOI were used because the other elements did not show any variability
S is represented in both first two components, it has been taken into account for discussion because of its geological relevance, Table 6 shows that the first component is given by S, Y, Rb, U and REE vs. Pb, V, S and LOI, which represents 48% of the total variance of the model, showing that these elements are related
Summary
The mobility of major, minor and rare-earth elements (REE) during alteration processes in different environments has been documented by numerous authors and has been used to discriminate the origin of kaolin deposits. (Sturchio et al, 1986; De Groot & Baker, 1992; Gouveia et al, 1993; van der Weijden & van der Weijden, 1995; Condie et al, 1995; Dill et al.,1997, 2000; Galan et al, 2007; Pandarinath et al, 2008, among others). The former being supergene or hypogene in orgin, have been documented These Patagonian deposits are derived from Mesozoic rhyolitic rocks. Because of the large amount of data, a statistical method was chosen to prove if the primary origin of these deposits can be discriminated from the behaviour of certain elements. Because of the large amount of data a multivariate statistical method, Principal Components Analysis (ACP), was used to determine which elements better characterize the deposits. The kaolin deposits examined in this study are located in four areas of Patagonia (Fig. 1), the Blanquita and Equivocada mines in the Province of Rıo Negro, the Estrella Gaucha mine and River Valley deposits in the Province of Chubut, and Lote 8 and Cerro Rubio in the Province of Santa Cruz. The Blanquita mine is characterized by the presence of kaolinite and alunite with scarce dickite and pyrophyllite, whereas in the Equivocada mine, kaolinite is associated with dickite and traces of alunite (without pyrophyllite) (Marfil et al, 2005)
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