Northward extrusion of the ultrahigh-pressure units in the southern Dabie metamorphic belt, east-central China

作者：Yamamoto Hiroshi^*; Terabayashi Masaru; Okura Hyugo; Matsui Takashi; Kaneko Yoshiyuki; Ishikawa Masahiro; Maruyama Shigenori

来源：Island Arc, 2013, 22(1): 51-62.

DOI：10.1111/iar.12004

• Dabie
• exhumation
• shear sense
• structure
• ultrahigh-pressure

The Dabie orogenic belt in central China extends along the Triassic suture between the SinoKorean and Yangtze cratons. The structure of the metamorphic rocks have been investigated in the ShimaWumiao area near the southeastern end of the Dabie orogenic belt. Detailed mapping revealed that the metamorphic sequence in this area can be subdivided into four subhorizontal lithotectonic units. These units are denoted by I, II, III, and IV in the order of structural bottom to top. Unit I is composed of felsic gneiss, eclogite, and minor pelitic gneiss. Unit II consists of felsic gneiss and eclogite with coesite pseudomorphs. Unit III consists of felsic gneiss, pelitic gneiss, metacarbonate, and eclogite with occasional coesite inclusion. Unit IV is composed of felsic gneiss, amphibolite, and minor pelitic gneiss. Those metamorphic rocks underwent penetrative ductile deformation which is denoted by gently south-dipping or subhorizontal foliation and NNW-trending mineral lineation. Deformation microstructures in oriented samples from Units I and II indicate consistent northward displacements of the hanging wall and those from Units III and IV indicate southward displacements. The subhorizontal structure and opposite shear directions between Units III and Units IIIIV suggest northward extrusion of UHP metamophic units (II and III). The subduction polarity could be opposite to the extrusion trend. The UHP metamorphism in the Dabie orogenic belt is attributable to southward subduction of the SinoKorean craton beneath the Yangtze craton.

• 出版日期2013-3