Grant: Discovery Grants Program - Individual

Earth history has seen a sequence of supercontinents forming when continents collide, then breaking up a few hundreds of millions of years later, driven by forces in the Earth's mantle. This project tests the hypothesis that at least two examples exist of supercontinents experiencing a huge amount of volcanism and related processes shortly before breaking apart, in the form of linear belts of this activity right across their interiors, from end to end. In the case of Gondwana, the largest part of Pangaea, a belt of the resulting rocks - 183 million years old - is known to extend from Tasmania in Australia, through Antarctica, and into South Africa and Botswana. I will test the extension of these rocks into Brazil and West Africa (Côte d'Ivoire and Liberia), which would establish a linear track of volcanic activity about 14,500 km long - a third of the circumference of the Earth - being created just before Gondwana broke up and the Atlantic Ocean began to open. A much older supercontinent, Nuna, which existed about 1.5 billion years ago, may have evidence of a similar event. Rocks that preserve the transport of magma within the crust 1,330 million years ago in Labrador, throughout the Canadian Arctic, into Siberia, northern Australia, and northern China appear to define another linear belt about 9,000 km long when the continental pieces of Nuna are reconstructed. The end-points of this proposed belt are already well-described; I will fill in the gaps through the Canadian north to test whether this is another example of enormous volcanic activity through the heart of a supercontinent before its break-up. I will use high-precision age dating (using the uranium-lead method on the minerals zircon and baddeleyite) to link the proposed components of these belts through their age. Their relationship to the melting processes in the Earth's mantle that generated the magma will be tested using the chemical and isotopic composition of the rocks themselves. This work presents the opportunity to study the effects of the presence of supercontinents on the mantle; the effects of such huge outpourings of lava and magma on the atmosphere and biosphere; and the connectivity of regions that are known to host natural resources such as economic mineral deposits. Three Master's students and one PhD student will be trained in this study, some focussing their work on local elements and some doing field work in the Canadian North to collect new samples that will increase the scale of the igneous systems being studied. They will gain experience in state-of-the-art clean lab methods as well as field techniques in remote areas, and connect with a network of collaborators from around the world.