A deep section of accretionary complex: Susunai Complex in Sakhalin Island, Northwest Pacific Margin

• Published in: The Island Arc
• Main Authors: Kimura, Gaku, Sakakibara, Masayuki, Ofuka, Hisashi, Ishizuka, Hideo, Miyashita, Sumio, Okamura, Makoto, Melinikov, Olex A., Lushchenko, Vilera
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1992
• Subjects: Sakhalin; Alaska
• Online Access: http://dx.doi.org/10.1111/j.1440-1738.1992.tb00067.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1440-1738.1992.tb00067.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1440-1738.1992.tb00067.x

Abstract A deep section of accretionary complex, the metamorphosed Susunai Complex, is observed on Sakhalin Is., Russia. High pressure part of pumpellyite‐actinolite facies metavolcanics, metacherts and metapelites are well exposed and constitute a tectonic pile preserving primary structures related to underplating of the oceanic crust. Three stages of deformation, D 1 through D 3 , suggest successive deformation during subduction, underplating and exhumation of the complex. Oceanic material in the complex is more abundant than other well documented ancient accretionary complexes (e.g. the Shimanto Belt in southwest Japan and the Ghost Rocks Formation in Alaska), which were shallowly underplated. At Susunai, deep down‐stepping of a décollément has scraped off the upper part of the oceanic crust, primarily the pillowed basalt horizon. This down‐stepping results from crustal weakening as overpressured water is released from the fractured oceanic crust during metamorphism.