Duplex of metamorphic units including ultramafic rocks in the central region of T okunoshima, S outhwest J apan

A unique geological duplex featuring serpentinite, dioritic gneiss, and amphibolite layers was discovered in the central region of Tokunoshima Island, part of the Amami Islands in Southwest Japan. This tectonic stack, characterized by northwest-dipping metamorphic units intercalated with pelitic schist, provides evidence of top-to-the-east, southeast, or south displacements under ductile deformation conditions. The study suggests that this serpentinite-bearing duplex formed due to tectonic erosion and accretionary growth in a Cretaceous or older subduction zone. Notably, the metamorphic rocks in Tokunoshima exhibit low-pressure and high-temperature amphibolite-facies metamorphism, distinct from other regions of the Shimanto Belt and neighboring islands. This discovery challenges existing geological models and highlights the unique metamorphic history of Tokunoshima.

Ueda, S., Yamamoto, H., & Terabayashi, M. (2017). Duplex of metamorphic units including ultramafic rocks in the central region of Tokunoshima, Southwest Japan. Island Arc, 26(4). Portico. https://doi.org/10.1111/iar.12199