Abstract

Geological knowledge is basic for the study of our Planet and its contents, being related to the analysis of minerals and rocks, the processes and mechanisms that act on the components of the Lithosphere and, therefore, with all the aspects that reflect the History of the Earth over time. In order to study the rocks, it is necessary to start with a petrographic analysis of the minerals, since it allows identifying them and also determining their main characteristics. The X-ray analysis allows distinguishing the structures and crystalline phases through the use of X-ray diffraction and the elemental analysis by X-ray fluorescence. This work presents some modern applications instead of the traditional analytic routines, treating portable equipment, which allows developing a multi-elemental analysis in a fast and easy way. Finally, some conclusions related to the application of the method on granite have been extracted.

1. Introduction

A rock can be transferred from a genetic group to another as a consequence of physical or chemical changes, such as the weathering/erosion that can affect an igneous rock and turn it into sediments.

There are three ways to investigate a mineral or a rock: macroscopically, microscopically or by means of geochemical methods (Skoog & Leary, 2004).

The most simple and economical option is the macroscopic approach. The description of the rock is made by the direct use of the naked eye and some simple tools (a magnifying glass, hydrochloric acid, a piece of glass, etc.). This allows describing features such as texture, fabrics, density, hardness, brightness, morphology, exfoliation (fracturing), type of minerals conforming the sample, etc.

When using microscopic recognition, a special microscope and a treated sample (thin section) are required. It is the most adequate method to employ after the macroscopic study.

Chemical analyses are performed in special laboratories. There are several types of geochemical analyses. The most important are X-ray fluorescence and diffractometry. Special equipment is used in both cases, and it is necessary a previous sample preparation.

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