Based on the field survey data of the Guangxi offshore voyage in May 2021, the distribution characteristics of the wind field during the spring monsoon transition period, the temporal and spatial changes in the diluted water path, and the corresponding ecological responses were analyzed. The results show the following: the core region of diluted water is located along the coast of Guangxi, and the diluted water expands to the east and west at the same time, where the thickness of the diluted water reaches 20 m. Under the combined action of the easterly wind and westward current, the westward expansion trend was stronger than the eastward expansion trend. The surface distribution of suspended solids, chlorophyll a, dissolved oxygen, and active silicon is similar to the dispersion range of the diluted water, and the high-value areas all appear near the estuary, which is basically consistent with the salinity distribution in the core region of the diluted water. Under the mixing caused by the wind and tide in the estuary area, the difference in dissolved oxygen between the surface and bottom layer is small, while in the nearshore area, the stratification of seawater hinders the dissolved oxygen’s downward transmission, resulting in a large difference in dissolved oxygen between the bottom and the surface.

Slab windows represent regions within the mantle that are largely devoid of slab material, facilitating direct communication between the mantle above and below the subducting slab. This unprecedented interaction disrupts the conventional material-energy exchange mechanisms between the subducted slab and mantle wedge, giving rise to anomalous heat flow, distinct magmatism, metamorphism, and geophysical features. Geochemical analyses of samples collected from the southern margin of the Parece-Vela Basin have illuminated the magmatic processes associated with a slab window. C20-3 is indicative of a hot and dry mantle upwelling that occurs through the slab window. On the other hand, C20-1 signifies an adakitic rock, which originates from the melting of oceanic crust at the periphery of the slab window. Slightly east of the slab window, C21-1 reveals evidence of a heated depleted mantle, influenced by the hot and dry mantle upwelling through the slab window. Additionally, a common Island Arc Basalt (IAB), denoted as C21-2, was also observed in the island arc region. Topographical data highlights the irregular distribution of numerous seamounts between the West Mariana Ridge and the Parece-Vela Basin spreading center. Seismological records reveal a preponderance of strike-slip earthquakes in the southern seamount region, alongside exceptionally high heat flow measurements at the northwest extremity of this area. The shape of the slab window can be roughly modeled by analyzing the distribution of earthquakes. Collectively, these observations lead us to postulate the existence of a slab window beneath the southern rim of the Parece-Vela Basin, likely attributed to the tearing of the subducting Pacific Plate along the strike-slip fault situated between the Ulithi and Fais Atolls.