大别山高压-超高压变质期后伸展构造格局

大别山高压、超高压变质期后构造格架的最显著特征是以罗田片麻岩穹隆为核部的多层伸展拆离滑脱带的发育，并由它们将超高压变质单元、高压变质单元和蓝闪－绿片岩单元分隔成垂向叠置的席状岩片，类似于变质核杂岩的基本结构样式。这种伸展构造格架制约了高压、超高压岩石的展布，而在较大榴辉岩体中保存的缩短或挤压组构则是以高压、超高压变质作用为标志的陆－陆碰撞事件的记录。正确地区分挤压组构与伸展组构是识别大别山带内高压

EXTENSIONAL TECTONIC FRAMEWORK OF POST HIGH AND ULTRAHIGH PRESSURE METAMORPHISM IN DABIESHAN, CHINA

The most prominent feature of the extension tectonic framework of post high and ultrahigh pressure metamorphism in Dabieshan is the development of the multi_layered extension detachment zones surrounding the core of the Luotian dome, and the separation of the UHP, HP and epidote blueschist units by the detachment zones, forming the vertically stacking sheet_like slices of the high and ultrahigh pressure metamorphic rocks, similar to the structural style of metamorphic core complex. The extension tectonics of post HP and UHP metamorphic event constrains the distribution and present configuration of the HP and UHP metamorphic rocks. However, the shortening and compression fabric preserved in the larger eclogite bodies is the record of continent_continent collision event marked by HP and UHP metamorphism. Correctly discriminating the compressional and the extensional fabrics is one of the key problems in the study of the geodynamic process of the formation and exhumation of HP and UHP metamorphic rocks. It is suggested that the partial melting happened in the DGC and UHP unit contemporaneous with the extrusion of UHP metamorphic rocks into the lower_middle crust, and the formation and emplacement of the migmatite and granites are the response to the change in thermal state, facilitating the transfer from the compressive regime to extension regime in the crust. The large_scale crustal extension and uplift and the accompanying anatexis in Dabieshan are probably related to the delamination and magmatic underplating in the mantle and the lower crust.