Predictive geochemical and geodynamic models of plume-lithosphere interaction

The majority of Earth’s volcanism is concentrated at tectonic plate boundaries, where plates move away from one another to create mid-ocean ridges, or where one plate slides beneath another to form a subduction zone. However, an important and widespread class of volcanism occurs within plates, or across plate boundaries. These so-called intra-plate volcanic provinces, which include the most rapid and voluminous volcanic episodes recorded in Earth’s history, are often associated with mantle plumes, hot buoyant columns that rise from Earth’s core-mantle-boundary to its surface. Mantle plumes are responsible for many of the volcanic tracks that extend across the Australian continent (e.g. Davies et al. 2015a) and have also played a central role in: (i) the evolution of Earth’s surface and its deep interior; (ii) global mass extinction events (e.g. Sobolev et al. 2011); (iii) initiating the seafloor spreading that produced many of the world’s oil and gas basins (e.g. Hill, 1991); and (iv) the genesis of large nickel, platinum and diamond deposits (e.g. Torsvik et al. 2010). Nonetheless, despite the significance of plume-related magmatism, both regionally and globally, a key aspect of the relationship between mantle plumes and surface volcanism remains enigmatic: the mechanism by which a rising plume interacts with, and eventually displaces the lithosphere – Earth’s rigid outermost shell - to reach the low-pressure regime required for melting, is not understood. As a result, it is impossible to interpret the geological record of mantle plumes, which is critical if we are to understand the origin of Earth’s intra-plate volcanic provinces, their associated volcanic hazard, the long-term evolution of Earth’s surface and interior, and the role of plumes in global mass extinction events, continental-breakup and mineralization.

In this project, state-of-the-art geodynamical models from Fluidity, alongside a novel predictive geochemical tool, will be used to answer two far-reaching questions:

  1. How do mantle plumes interact with and eventually displace the overlying lithosphere.
  2. How­­ does this displacement impact on the extent, rate and volume of partial melting, and how is this reflected in the geological record?

Results will be validated via comparisons with observed melt volumes, melt production rates and melt compositions, with a particular emphasis on the Kalkarindji LIP in Australia. Results, nonetheless, will be globally applicable, allowing us to relate, for the first time, wide-ranging geological and geochemical observations from intra-plate volcanic provinces at Earth’s surface to the underlying driving mechanisms, in an Earth-like, geodynamical framework.