SEG DISTINGUISHED LECTURE: SELF-ORGANIZED SYSTEMS AND ORE FORMATION—THE KEY TO SPATIALLY-PREDICTIVE TARGETING?

It is proposed that ore forming systems are examples of self-organized critical systems, in the sense of Bak et al (1987). Several lines of evidence support this hypothesis: the power-law size frequency distribution of mineral deposits; their fractal spatial distribution, their epsisodic multicylcic nature and their spatial association with barriers to advective flow such as antiformal seals, and commonly periods of compressional deformation. This concept has very important implications for spatially-predictive mineral targeting, both at the regional and deposit scale. In particular, it emphasises that a local threshold barrier to fluid/magma flow is an absolutely essential ingredient for an ore forming system. This important practical implication of the SOC system model is not included within the current dominant paradigm for understanding mineral systems: that is source-trap-transport. There are several other important practical implications of these ideas. One of the more important is that the existing paradigm for applying strutural targeting in mineral exploration, which emphasizes zones of dilatancy related to fault kinematics and geometry, is incorrect. Instead ore fluids and magmas essentially create their own conduit zones between source and sink, utilising whatever structural architecture they encounter on their way.