Metallogeny of modern and ancient oceans

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The discovery of metal-depositing hot springs at volcanoes on the seafloor, and especially the link to chemosynthetic life, was one of the most compelling scientific advances of the 20th century. 80% of the world's active volcanoes occur in the oceans, and the volcanic and hydrothermal activity is now recognized as having a critical role in the sulfur, carbon and metal cycles of the marine environment. However, important questions remain about the diversity of seafloor hydrothermal systems, the flux of metals from different sources, and the history of metal loading to oceans from hydrothermal vents. Seafloor volcanism was even more prevalent in Earth's ancient oceans, and the associated hydrothermal activity was responsible for many of the world's largest and most valuable mineral deposits. However, the underlying geodynamic factors controlling the distribution of these resources are not fully understood. To address some of these questions, we are participating in an international effort to explore and document hydrothermal activity in a variety of different volcanic and tectonic settings in the oceans. The specific objectives of the research are: (i) to identify different sources, sinks and transport pathways for metals in modern seafloor hydrothermal systems, (ii) to quantify the natural loading of metals to the oceans from different hydrothermal sources, including those metals with potentially lasting far-field environmental significance, (iii) to compare present-day fluxes of metals with the geological record of past metal accumulations on the seafloor, and (iv) to improve models of the metal inventory of both modern and ancient volcanic terranes. These objectives will be achieved through a program of seafloor mapping and sampling, related laboratory studies, and field work on ancient ore deposits. Data from this research will contribute to new models of the geochemical evolution of Earth's oceans and will have direct practical application in the exploration for land-based mineral resources.