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摘要:
俯冲侵蚀是一种将地壳及岛弧物质从弧前搬运走的地质过程，会导致弧前物质的缺失，这种地质过程普遍地出现在汇聚型板块边缘。雅浦海沟位于加罗林板块与菲律宾海板块之间，是一个活跃的俯冲带。利用2015年中科院海洋所在西太平洋雅浦海采集的最新的多波束和地震数据，给出了雅浦海沟发生俯冲侵蚀的直接证据：(1)雅浦海沟具有异常短的沟弧间距(41 km)；(2)海沟呈不对称的“V”字形，增生楔缺失；(3)俯冲板片基底起伏程度大，加罗林洋底高原上洋脊、海山、地垒地堑构造发育；(4)海沟内壁斜坡较陡，弧前斜坡坡度的平均值约8.69°，雅浦海沟的弧前增生楔缺失。揭示了雅浦海沟南北两侧俯冲侵蚀模式的差异，北部的俯冲侵蚀主要由于洋底高原上地垒地堑与上覆板块的摩擦造成，板块之间可能不是直接接触，存在“剥蚀带”；南部的俯冲侵蚀主要由于洋底高原上的海山与上覆板块的摩擦造成，板块之间可能是直接接触的。
Abstract:As a specific geological process, subduction erosion can move the substance of the earth crust and arc away from the forearc wedge and cause the missing of forearc crustal material, which generally occurs at the convergent plate boundaries. The Yap trench is an active subduction zone which is located at the convergence zone of the Caroline Plate and Philippine Sea Plate. According to the new multi-beam and seismic data that acquired by the integrated geophysical survey off the Yap Island, western Pacific, conducted by Institute of Oceanology, Chinese Academy of Sciences, we found evidence of erosion as follows: (1)The Yap trench has unusually short distance to the arc from the trench axis (41 km); (2)The cross-sections across the axis show asymmetry V-shape and the accretionary wedge is absent in the trench; (3)The relief of oceanic basement is severe, because ridges, sea mountains, structural belt of horst and graden exist in the oceanic plateaux of Caroline Plate; (4) The trench wall exhibits a steep slope and the mean forearc slope is 8.69° and the accretionary wedge is missing. We speculate that the mode of subduction erosion is different on both sides of the Yap trench. The subduction erosion of oceanic plateau in the northern Yap trench is mainly resulted from the friction between the structural belt of horst and graben and the overlying plate, and the structural belt of horst and graben initially might be filled with sediment, so there is a zone of basal erosion between the plates rather than direct contact; However, the subduction erosion of oceanic plateau in the southern Yap trench is mainly resulted from friction between the seamounts and overlying plate and the two plates contact directly.
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