The concepts of fractal have been used widely in the field of earth sciences for characterizing geological quantities and objects with self-similarity. It has been shown that fractal modeling often provides powerful tools for characterizing underlying spatial distribution structure of geological quantities and objects. This paper develops a method to test and quantitatively assess the presence of n-dimensional self-affine fractals and explains the method procedure of n-dimensional self-affine fractals in application and real meaning of fractal dimensions by examples. The fractal dimensions can be regarded as the quantity index to reflect the variety degree of region variable on certain direction. The method not only is applied to Au data and Ag data but also suited for other geochemical element data or geological data and has general meaning.