Fundamental Advances in Economic Geology
Analyses of temporal and geographic distributions of the minerals of beryllium, boron, copper, mercury, and molybdenum reveal episodic deposition and diversification. We observe statistically significant increases in the number of reported mineral localities and/or the appearance of new mineral species at ~2800 to 2500, ~1900 to 1700, ~1200 to 1000, ~600 to 500, and ~430 to 250 Ma. These intervals roughly correlate with presumed episodes of supercontinent assembly and associated collisional orogenies of Kenorland (which included Superia), Nuna (a part of Columbia), Rodinia, Pannotia (which included Gondwana), and Pangea, respectively. In constrast, fewer deposits or new mineral species containing these elements have been reported from the intervals at ~2500 to 1900, ~1700 to 1200, 1000 to 600, and 500 to 430 Ma. Metallogenesis is thus relatively sparse during periods of presumed supercontinent stability, breakup, and maximum dispersion.
Variations in the details of these trends, such as comparatively limited Hg metallogenesis during the assumed period of Rodinia assembly; Proterozoic Be and B mineralization associated with extensional environments; Proterozoic Cu, Zn, and U deposits at ~1600 and 830 Ma; and Cenozoic peaks in B, Cu, and Hg mineral diversity, reveal complexities in the relationship between episodes of mineral deposition and diversification on the one hand, and supercontinent assembly and preservational biases on the other. Temporal patterns of metallogenesis also reflect changing near-surface environments, including differing degrees of production and preservation of continental crust; the shallowing geotherm; changing ocean chemistry; and biological influences, especially those associated with atmospheric oxygenation, biomineralization, and the rise of the terrestrial biosphere. A significant unresolved question is the extent to which these peaks in metallogenesis reflect true episodicity, as opposed to preservational bias.