Abstract
It is presented the results obtained of a multivariate statistical analysis concerning the chemical and phase composition, as a characterization purpose, carried out with 52 rock phyllite samples selected from the provinces of Almeria and Granada (SE Spain). Chemical analysis was performed by X-ray fluorescence (XRF). Crystalline phase analysis was performed by X-ray powder diffraction (XRD) and the mineralogical composition was then deduced. Quantification of weight loss (100? and 1000?C) was carried out by thermal analysis. The aims of this investigation were to analyze and compare the chemical and mineralogical composition of all these samples and to find similarities and differences between them to allow a classification. Several correlations between results of the characterization techniques have been also investigated. All the data have been processed using the multivariate statistical analysis method. The XRF macro-elements (10) and microelements (39) data generate one macrogroup with two new subgroups (1 and 2), and an isolated sample. In subgroup 1 of macroelements, a positive correlation was found between XRF results and geographic location characterized by lower MgO content, which is associated to its geological origins. When multivariate statistical analysis is applied to results obtained by XRD, two groups appear: the first one with a sample with zero percentage of iron oxide and the second one with the rest of the samples, which is classified in two groups. A correlation is observed between the alkaline content (XRF) and illite (XRD), CaO and MgO with dolomite and indirectly between the weight loss after heating at 1000?C and the contents of phase minerals that lose structural water (illite + chlorite) or carbon dioxide (dolomite). The present investigation has interest and implications for geochemistry and analytical chemistry concerning earth rocks and silicate raw materials.
Highlights
Phyllites are foliated and metamorphized rocks with a low degree of schistosity
In subgroup 1 of macroelements, a positive correlation was found between X-ray fluorescence (XRF) results and geographic location characterized by lower MgO content, which is associated to its geological origins
When multivariate statistical analysis is applied to results obtained by X-ray powder diffraction (XRD), two groups appear: the first one with a sample with zero percentage of iron oxide and the second one with the rest of the samples, which is classified in two groups
Summary
Phyllites are foliated and metamorphized rocks with a low degree of schistosity. They can occasionally contain calcite, besides quartz, moscovite, talc, albite and chlorite, among other minerals. They have a silky sheen and feel greasy to the touch in a similar way to talc. They flake and have relatively little cohesion. Their colours vary from grey, greenish-grey, bluish-grey, violet or even brown or reddish [1,2,3].
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