We report on the optical properties in the dielectric regime of gold nanostructured granular thin films fabricated through sputter deposition with a composite target at room temperature and over a wide photon energy range (0.62-4.13 eV) by means of Spectroscopic Ellipsometry. The thickness and the films effective optical constants are successfully determined using an approach based on multiple Gaussian oscillators. In the quasi-static regime, i.e., 2R << lambda, and in the dipole approximation, examining the real and imaginary parts, epsilon(1), epsilon(2), of the dielectric function, it is shown that the dc optical conductivity is almost negligible (sigma = omega epsilon(0)epsilon(2) <<10(-5) Omega cm(-1)) and only the capacitive contribution holds for the electron-phonon relaxation in localized surface plasmon of the gold particles. Furthermore, we find that the resonant frequencies omega(p) becomes red-shifted when the particles are electromagnetically coupled to each other or when the surrounding medium dielectric constant, epsilon(m) , increases, thus exhibiting a wide spectral tuning range of 1.95-2.24 eV. (C) 2017 Elsevier B.V. All rights reserved.