Involvement of Slab‐Derived Fluid in the Generation of Cenozoic Basalts in Northeast China Inferred From Machine Learning

Abstract

The origin and involvement of fluid in the generation of Cenozoic basalts in Northeast China are still under debate. Here we apply the machine learning methods of random forest and deep neural network to train models using data sets of global island arc and ocean island basalts. The trained models predict that most Cenozoic basalts in Northeast China are influenced by fluid and that the fluid activity decreases from east to west. The boundary defined by fluid activity coincides with the westernmost edge of the present-day stagnant Pacific slab determined by seismic tomography and with the geochemical boundary defined by magnesium isotopes. These observations support the view that the fluid involved in the generation of the basalts is controlled by the stagnant Pacific slab instead of driven by the plume induced by the sinking Izanagi Plate.\nPlain Language Summary Many volcanoes are erupted in Northeast China, and it is of great interest to study the origin of these volcanoes. Previously, the chemical compositions of these volcanoes and typically elemental ratios such as Ba/Th are used to find the answer. In the present study, modern machine learning methods called random forest and deep neural network are used to do the work. The advantage of the new methods is that they can obtain a whole picture of the chemical compositional data instead of a particular one from an elemental ratio. The new methods find that the generation of these basalts is closely related to the Pacific slab, subducting downward at Japan, reaching similar to 600-km depth at the border of eastern China, and extending horizontally to the Mongolia border. Materials released from the slab, such as fluid and melt and the elements dissolved in them, move upward and trigger the volcanoes we see on the surface. The boundary between volcanoes affected dominantly by the slab-derived fluid and those that are not coincides with the westernmost edge of the deeply buried Pacific slab. These findings deepen our understanding of the generation of these volcanoes.