Scientific drilling plan targets the Huatung basin to reveal the Mesozoic tectonic evolution of the western pacific
image: The yellow square denotes the extent of Fig. 2. Red circles in the PSP represent the locations of DSDP drill holes (after Karig et al., 1975; deVries Klein et al., 1980; Kroenke et al., 1980). Circles in the SCS indicate the drill hole locations of ODP Leg 184 (orange), IODP Leg 349 (red), and IODP Leg 367/368 (yellow) expeditions (after Wang et al., 2000; Li et al., 2014; Jian et al., 2018; Sun et al., 2018). Red numerals mark DSDP station numbers; the white arrow shows the direction and velocity of the PSP with respect to the Eurasian plate (Hsu et al., 2016). Bathymetric data are derived from the GEBCO_2025 Global Bathymetric Grid of the GEBCO (General Bathymetric Chart of the Oceans) project (https://www.gebco.net/data-products/gridded-bathymetry-data).
Credit: ©Science China Press
The Mesozoic tectonic history of the western Pacific, a critical period for understanding Earth’s plate evolution, contains many missing links. The Huatung Basin, situated at the complex junction between the Philippine Sea Plate and the Eurasian Plate, is considered a crucial area for filling these gaps, as it may be a remnant of an ancient ocean basin. However, decades of research have left its exact age and nature unresolved due to a lack of direct rock samples.
A new paper published in Science China Earth Sciences by a team led by Prof. Minghui Zhao from the South China Sea Institute of Oceanology, Chinese Academy of Sciences, proposes a targeted strategy to solve these geological puzzles. The study synthesizes years of geophysical data, revealing that the Huatung Basin possesses atypical oceanic crust—about 5–7 km thick with a distinct high-velocity layer in the lower crust—which differs from the neighboring Cenozoic West Philippine Sea Basin. Further complicating the picture is the Gagua Ridge, located to the east, which exhibits a much thicker crust (12–18 km) and has several competing origin hypotheses, including being a remnant of an ancient spreading ridge, a product of strike-slip compression, or a failed subduction zone.
To directly test these hypotheses and retrieve definitive evidence, the research team designed a four-site drilling plan tailored for China's new state-of-the-art ocean drilling vessel, the Mengxiang. The four proposed sites are located at key tectonic positions, forming a logical chain of investigation:
Site A (center of the Huatung Basin): The primary goal is to drill into the igneous basement and recover basalt samples. This would provide the first direct, radiometric age for the basin, definitively confirming whether it is a Mesozoic ocean basin.
Site B (northern Luzon Arc): This site aims to understand the tectonic transition from subduction to collision between the South China Sea and the Huatung Basin, by analyzing the sedimentary sequences that record this dynamic process.
Site C (crest of Gagua Ridge) and Site D (basin east of Gagua Ridge): This paired approach is designed to resolve the enigma of the Gagua Ridge. By sampling the ridge's basement (Site C) and the basin to its east (Site D), scientists can distinguish between the competing origin theories and clarify the ridge's tectonic relationship with the surrounding structures.
The study emphasizes that this project is not just about answering fundamental scientific questions. It represents a critical scientific opportunity for China to leverage its self-developed drilling capabilities to lead a new phase of international ocean drilling, potentially rewriting the understanding of western Pacific plate tectonics and playing a significant role in Earth system science.
Zhao M, Zhu J, Zhang G, Sibuet J-C, Cheng J, Zhong G, Gao H. 2026. Geodynamic evolution of the Huatung Basin and future ocean drilling sites selection. Science China Earth Sciences, 69(7): 2750–2761, https://doi.org/10.1007/s11430-025-1915-0