Rock Physics Analysis of Volcanic Lava Flows and Hyaloclastites

Summary A study is conducted to investigate the rock physics properties of volcanic facies from available core measurements (72 samples available from Iceland and Hawaii). The main goal is to investigate the rock physics properties of a set of volcanic rock samples, and to establish predictive rock physics templates for these rocks, as a function of facies and rock texture, fluids and minerology. We focus on lava flows and hyaloclastites from Iceland and Hawaii. We find that both these facies can be modelled using modified Hashin-Shtrikman upper elastic bounds, and we create rock-physics templates for varying porosity and fluid saturations. Dry or gas-filled hyaloclastite facies plots with low acoustic impedances and low Vp/Vs ratios and are nicely separated from brine-filled hyaloclastites. Dry and wet high-porosity/high-permeability vesicular lavas will have similar AI and Vp/Vs values, and therefore these rocks will be more difficult to discriminate seismically.