New Â鶹ֱ²¥-led research has uncovered how rocks sourced from the Earth\u2019s mantle are linked to the formation and breakup of supercontinents and super oceans over the past 700 million years, suggesting that the Earth is made up of two distinct \u2018faces\u2019.<\/p>\n
The research, published in the leading Journal Nature Geoscience<\/em>, examined the chemical and isotopic \u2018make-up\u2019 of rocks sourced from thousands of kilometres below the surface to better understand how the Earth\u2019s mantle responds to plate movements that occur near its surface.<\/p>\n Lead author Dr Luc-Serge Doucet, from the Earth Dynamics Research Group in Curtin\u2019s School of Earth and Planetary Sciences, said the Earth’s mantle is currently divided into two main domains, African and Pacific, but little is known about their formation and history and they are commonly assumed to be chemically the same.<\/p>\n \u201cOur team used trace metals such as lead,\u00a0strontium,\u00a0and neodymium, from hotspot volcanic islands\u00a0including the\u00a0Hawaiian islands in the Pacific Ocean\u00a0and the\u00a0La Reunion island in the Indian Ocean, to examine whether these two domains have the same chemical \u2018make-up\u2019,\u201d Dr Doucet said.<\/p>\n \u201cWe found that the African domain was \u2018enriched\u2019 by subducted continental materials, which was linked to the assembly and breakup of the supercontinent Pangaea, whereas no such feature was found in the Pacific domain.\u201d<\/p>\n The team found that the contents of the two mantle domains are not exactly the same as previously thought. Instead, the Earth appears to have two chemically distinct hemispheric \u2018faces\u2019, with the Pacific ring of fire being the surface expression of the boundary between the two.<\/p>\n Co-author John Curtin Distinguished Professor Zheng Xiang Li, head of the Earth Dynamics Research Group, said the two chemically distinct hemispheres discovered by the team can best be explained by the distinct evolutionary histories of the two mantle domains during the Rodinia to Pangaea supercontinent cycles.<\/p>\n \u201cWe found that the African mantle domain contains continental materials, which were brought down by the subduction system for at least the past 600 million years. However, the Pacific mantle domain has been protected from the infiltration of such materials,\u201d Professor Li said.<\/p>\n \u201cOur research findings are significant as they showcase a dynamic relationship between plate tectonic processes that operate near the surface and the formation and evolution of Earth\u2019s deep mantle structures.<\/p>\n \u201cThe work helps us to understand what drives plate tectonics and the formation and reservation of global geotectonic features such as the Pacific ring of fire. The dynamic and interactive nature of the entire Earth system has important implications on the formation of Earth resources, the evolution of Earth environment, and even the evolution of life.\u201d<\/p>\n The research was co-authored by researchers from Curtin\u2019s School of Earth and Planetary Sciences, Tanta University in Egypt, St Francis Xavier University in Canada, Universit\u00e9 Libre de Bruxelles in Belgium, Queen\u2019s University in Canada, and the Chinese Academy of Sciences in Beijing.<\/p>\n