Use of Fractal Analysis for the Discrimination of Volcanic Particles

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CareyEAR-0086963Juvenile volcanic particles form an important component of pyroclastic rocks in recent and ancient volcanic terrains. The identification of volcaniclastic deposits often relies on an analysis of such particles. Although significant progress has been made in linking qualitative aspects of particle morphology to different types of source eruptions and fragmentation processes, a quantitative method of particle classification has remained elusive. We propose to investigate the use of fractal geometry as a quantitative method of volcanic particle discrimination. Volcanic particles are particularly well suited for the application of fractal analysis owing to their complex shapes and presence of re-entrants on their boundaries. We have developed a new technique based on the quantification and statistical analysis of discrete fractal elements in the outlines of volcanic particles. Preliminary work on this technique has shown excellent potential for quantitative discrimination of different volcanic particles. We propose to carry out fractal analysis on a suite of well-characterized samples to build up a matrix of fractal characteristics that will be representative of a wide variety of volcaniclastic deposits. The samples will encompass magma types from basalt to rhyolite and fragmentation mechanisms that include primary volatile degassing, phreatomagmatism, and granulation by quenching with seawater. In addition, samples will be analyzed from deposits produced by different transport mechanisms such as pyroclastic fall, flow and surge. We anticipate that the results of the study will provide significant advances in the quantification of volcanic particle morphology and lead to the means of statistically discriminating particles of different origin. Such a technique will be valuable to workers seeking to interpret the nature of ancient volcanic activity from the characteristics of their resulting deposits. Furthermore, the detailed quantitative analysis of particle morphology may lead to new insights about the roles of various fragmentation processes during complex explosive eruptions involving both the degassing of primary volatiles and the interaction with external water.