Chapter 1: Spatial Periodicity in Self-Organized Ore Systems
The development of more predictive models for the distribution patterns of large ore deposits and districts is critical for future discovery success in mineral exploration. Some studies have suggested that the distribution of orogenic Au and porphyry Cu deposits appears ordered with a periodic spacing in some mineral provinces, but it remains unclear if spatial periodicity is a common feature of diverse mineral systems. We present evidence for spatial periodicity of large mineral deposit clusters along 20 major structural corridors from nine world-class mineral provinces with five ore deposit types (orogenic Au, porphyry Cu, sediment-hosted Cu and Zn-Pb-Ag, and diamondiferous kimberlites). For orogenic Au deposit clusters, spatial periodicity commonly occurs around 30 to 40 km (range 19–50 km) in the Eastern Goldfields (Australia), Abitibi (Canada), and Sierra Foothills (United States) provinces. Periodicity of moderate- to giant-sized sediment-hosted Cu deposit clusters occurs around 27 km in the Central African Copperbelt (Zambia, Democratic Republic of Congo). Large porphyry Cu deposit clusters show periodicity around 65 to 122 km in the American Cordillera (United States, Mexico, Chile). Large shale-hosted Zn-Pb-Ag deposit clusters have a periodicity around 116 km in the Carpentaria province (Australia). Finally, kimberlite clusters have a spatial periodicity around 121 to 237 km in southern and central Africa. We also observed a dual periodicity along some structural corridors, with smaller deposits located at half the spacing of giant deposits. Whereas the mineral provinces studied were selected on the basis that they seemed to show spatial periodicity, many other provinces worldwide do not appear to display spatial periodicity of ore deposits.
We link our results to the phenomenon of self-organization, which explains emergence of large-scale spatial (and temporal) order in complex systems as an effective mechanism to dissipate large energy gradients. As the best examples of spatial periodicity of ore deposits identified to date are associated with some of the world’s best endowed mineral provinces, it is possible that overall province endowment is linked to both the degree of self-organization and the magnitude of regional energy gradients. Further research is required to identify relevant underlying geologic causes for spatial periodicity. Nevertheless, we provide two case studies suggesting that the intersection of preexisting basement fault sets with at least semiregular spacing may be a common control on spatial periodicity of mineral deposits. Where spatial periodicity of mineral deposits is observed to occur, it can improve the predictive capacity of exploration models and ore discovery rates.