浅议古板块构造单元划分原则

板块构造理论是古板块分区的基础。古板块构造分区和命名必须有明确的时空概念。按照威尔逊旋回，大洋俯冲阶段的构造分带最复杂、最明显，应该以该阶段作为分区的时间区间，一级构造单元是岩石图板块，以大洋型蛇绿混杂岩带作为分区界线；二级构造单元以地壳性质作为分区原则，可分为过渡壳和陆壳，地壳性质依据蛇绿岩（套）、沉积建造、岩浆岩组合特征来综合判别；三级构造单元是在二级构造区内以沉积岩、火山岩、岩浆岩建造的显著差异为分区原则，如岛弧弧盆带内分为弧前隆起、弧前盆地、岛弧带、弧间盆地、弧后盆地，在陆壳区内分为稳定陆壳区及活动陆壳区。四级构造单元是在三级构造区内以构造形态或局部地质特征作为分区原则，分为复背斜、复向斜、断褶带、岩浆岩带、蛇绿混杂岩带等。

ON PRINCIPLE OF THE CLASSIFICATION OF PALAEO-PLATE TECTONIC UNITS

The theory of plate tectonics is the division of palaeo-plates. The division and naming of palaeo-plate tectonics require definite take-space conception. Since the structural zoning of oceanic subduction stage is the most complex and most obvious according to Welson cycle,so the subduction stage is regarded as the time boundary of division. The first-grade structural unit is lithosphere plate,bounded by ophiolite melange belt of oceanic type. The second-grade unit includes transitional zone (arc-basin zone)and continental crust zone,classified in principle of crustal property which is judged by ophiolites,sedimentary formation and magmatic association etc.. The third-grade unit is divided within the second-grade unit according to the obvious difference of sedimentary, volcanic and magmatic formations, for example, front-arc arching, front-arc basin, arc zone,inter-arc basin,back-arc basin are subdivided within the inland arc zone; stable continental crust zone and active contitental crust zone subdivided in the continental crust zone. The fourth-grade unit is subdivided according to the structural morpholosy and local geology within the third-grace unit,such as anticlinorium,synclinorium,fault-fold belt,magmatic belt,and ophiolit 'e malange etc..