GEOGRAPHY

Scientists reveal the formation mechanism of the ocean-floor plateau


Recently, the interforest team and collaborators of the Key Laboratory of Marginal Sea and Ocean Geology of the Chinese Academy of Sciences have made an important breakthrough in the study of the genesis mechanism of the Shatsky Rises in the western Pacific Ocean, the third largest ocean floor plateau in the world, revealing that the interaction between mantle plumes and mid-ocean ridges is the main controlling factor for its formation. The results were published in Nature Earth Sciences, and the results were published in the journal in a brief on the results.

A spatiotemporal evolution model of mantle plume interactions with mid-ocean ridges (black double lines at the top represent mid-ocean ridge positions, black arrows indicate the direction of plate expansion). Photo courtesy of the research team

The ocean floor plateau is a large-scale topographic uplift area on the seabed, which is the product of large-scale magmatic activity and belongs to the large igneous province in the ocean, which has an important impact on the earth’s climate evolution and biological extinction.

“The causal mechanisms of the ocean floor plateau have long been controversial. Lin Ma, co-corresponding author of the paper, said that there are two main points of controversy: one is that the “mantle column model” believes that the ocean floor plateau is formed by large-scale magmatic activity caused by high-temperature mantle plumes originating in the deep part of the mantle; the other is that the “plate model” believes that the ocean floor plateau is formed by the upwelling and decompression melting of heterogeneous mantle materials induced by plate expansion, without obvious temperature abnormalities.

The Shatsky Rises in the western Pacific, located at the intersection of mid-ocean ridges, are ideal areas to study the genesis mechanisms of the ocean floor plateau. Researchers analyze geophysical and geochemical data in depth and perform quantitative geodynamic simulations. The results show that only the interaction of the “mantle plume” and the “plate expansion” can explain the observed phenomenon in the study area.

Combined with the formation of the Shatsky Rise, the researchers revealed a two-step pattern of ocean floor plateau formation. In the first stage, the mantle stigma strongly mixed with the surrounding mantle, and large-scale magmatic activity occurred at the mid-ocean ridge, forming the Great Tamu volcano at the southwestern end of the seamount. In the second stage, the mixing of mantle tails and the surrounding mantle is weakened, and thicker oceanic crust can still form at the mid-ocean ridge, but the magma composition is similar to the geochemical characteristics of deep enriched mantles, such as the Papaning Ridge at the northeastern end of the seamount, and similar phenomena have been found in other hot spots on Earth such as Iceland, the Azores and Galapagos.

Lin pointed out that this study has important scientific significance for revealing the origin of the earth’s ocean floor plateau and understanding the temporal and spatial evolution process of the mantle plume. (Source: China Science News, Zhu Hanbin, Li Shu)

Related paper information:https://www.nature.com/articles/s41561-023-01286-0

https://www.nature.com/articles/s41561-023-01289-x



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