长乐—南澳构造带的变形—变质作用

DEFORMATION EVENT AND METAMORPHISM OF CHANGLE-NANAO TECTONIC ZONE

长乐—南澳构造带在中生代时期经历了多幕构造变形和多期变质作用。它们分别是:高角闪岩相变质作用—第一幕变形;低角闪岩相变质作用—第二幕变形;绿片岩相变质作用—第三幕变形。每一幕变形和每期变质作用均有各自的构造形迹和典型矿物共生组合。

During recent years, the author has studied the Changlc-Nan/ao tectonic zone situated along the coastal area of Fujian and Guangdong provinces, southeast China by the method of study of tectonic-rock formation-events in order to clarity the history of tectonic evolution and determine the relationship between deformation event and metamorphism. The results obtained that the tectonic zone underwent many times of tectonic deformation and relatively metamorphism during the period of late-Triassic to Jurassic. The main conclutions are as follows: (1) The upper-crust rocks and volcanic rocks formed at early-Palaeozoic in the tectonic zone underwent the process of descending from the crust surface to depth and then rising from depth to surface. During the process, the upper-crust rocks and volcanic rocks were deformed by three times of tectonism and relevant metamorphism and tended gradually to the stable state. Metamorphic mineral association and tectonic trace were different in each stage of tectonism and metamorphism. (2) The degree of metamorphism of the three stages dccrcasscd gradually from southeast to northwest, i.e. hornblende fades occurred along the coastal area and greenschist facics developed on the inland area, suggesting that the tectonism and metamor-phism of the coastal area was earlier than that of inland area during the rising process. (3) Three cpisodes of tectonism were characterized by the evolution from plastic deformation (or plastic rlow) to brittlcncss deformation, suggesting that the deformation environment changed gradually from depth-tectonic level to the crust surface.