| We present a high resolution study of the void space geometry of vesiculated basalts (porosities in the range 61% to 80%) from three dimensional digitized images obtained by synchrotron X-ray tomography. As the void space is composed of vesicles, the solidified remnants of expanding gas bubbles, the contact surface between coalescent vesicles represents a pore throat. We discuss a throat finding algorithm used in digital analysis to locate such contact surfaces. The algorithm requires a segmented image from which a medial axis skeleton has been computed. We present results for the distribution of vesicle volumes, contact surface areas, vesicle coordination number (the number of neighbors with which a vesicle has coalesced), and correlations between these observable. The distribution for contact surface area is log-normal (down to the resolution of an individual voxel); the distribution for coordination number is exponential; and the distribution of vesicle volumes is not simply characterizable. There are strong correlations between vesicle size/coordination number and vesicle size/contact surface area. |
