The Formation Mechanism of Petit-Spot Volcanoes and the Nature of the Lithosphere-Asthenosphere Boundary (LAB) 斑点火山的形成机制和岩石圈-软流圈边界(LAB)的性质

The petit-spot volcanoes discovered near the subduction zone's outer rise represent a new type of seafloor magmatic activity. These volcanoes are small in scale, appear in clusters, and are extremely young. The rock samples are dominated by EM1 alkaline basalt, with high porosity and rich volatile components. The origin of magma of petit-spot volcanoes and the dynamic processes related to magma upwelling are still in debate. This paper presents the characteristics of petit-spot volcanoes and summarizes the three models proposed by previous studies on the formation mechanism and magma sources of these unique volcanoes. Based on the latest findings showing the lithosphere-asthenosphere boundary (LAB) beneath the oceanic plate may contain melts, we infer that the petit-spot volcanoes likely contain the clues about the fundamental scientific question of the nature of LAB. On the other hand, the volcanic rocks are rich in CO, which likely is the volatiles responsible for melt generation in the asthenosphere and melt accumulation at LAB. Therefore, the petit-spot volcano may also account for an important part of the carbon cycle. Finally, this paper proposes a comprehensive multidisciplinary approach is needed to reveal the formation mechanism of such unique volcanoes.