Interactions among mid-ocean ridges, plumes and Large Igneous Provinces

Tuesday, 15 December 2015: 14:55
303 (Moscone South)
Joanne M Whittaker1, Juan Carlos Afonso2, Sheona M Masterton3, Dietmar Müller4, Paul Wessel5, Simon Williams4 and Maria Seton4, (1)University of Tasmania, Hobart, Australia, (2)Macquarie University, Sydney, NSW, Australia, (3)GETECH, Leeds, United Kingdom, (4)University of Sydney, Sydney, Australia, (5)University of Hawaii at Manoa, Honolulu, HI, United States
Plate tectonic motions are commonly considered to be driven by slab pull at subduction zones and ridge push at mid-ocean ridges (MORs), with motion punctuated by plumes of hot material rising from the lower mantle. Within this model, the geometry and location of MORs are considered to be independent from deeply sourced mantle plumes commonly implicated in the formation of Large Igneous Provinces (LIPs).

Here we reconstruct the absolute locations of LIPs and MORs relative to plume locations, and find that LIPs predominantly form episodically at specific locations of MOR-plume interaction. Analysis of MOR and continental diverging plate boundary locations since 180 Myr reveals that long-standing MOR-plume interactions are enabled by slowly migrating ridge systems.

We calculate how much mantle material was converted to oceanic lithosphere at the MORs and calculate that slowly migrating MORs have extracted large volumes of material from the same part of the upper mantle over periods up to 180 million years. The geochemical signatures of mid-ocean ridge basalts and seismic tomographic data show that upper-mantle temperatures are elevated at significant distances from ridge–plume interactions, indicating a far-field, indirect influence of plume–ridge interactions on the upper-mantle structure.

In summary, long-standing interaction between divergent plate boundaries and mantle plumes, leading to the formation of LIPs, occurs in a much more systematic way than previously appreciated. The interaction of the surface spreading system with deeply sourced mantle plumes is an overlooked yet important aspect of the mantle circulation system, with likely implications for understanding a range of Earth system processes, such as evolution of the plate-mantle system, supercontinent assembly and dispersal, and patterns of ridge morphology and geochemistry.