冕宁三代褶叠层构造的发现及成因分析

DISCOVERY AND GENESIS OF FOLDING LAYER STRUCTURE IN SANDAI, MIANNING

位于扬子地台西缘的冕宁三代地区，出露有震旦纪一晚二叠世的沉积岩及火山岩，岩石普遍遭受了低绿片岩相变质和浅－中构造相变形，尤以顺层片理、顺层掩卧褶皱、顺层韧性剪切带最为发育，地层序列正常。它们是地壳伸展机制下的褶叠层构造组合，它发生于晚二叠世，定型于三叠纪。

Sandai area in Mianning County lies in the western margin of Yangtze Platform. Sedimentary and voleanic rocks from the Sinian to the Late Permian are exposed in the area. Most of the rocks underwent metamorphism of low greenschist facies and low-and medium-deformation characterized by bedding schistositization, bedding flat-lying folding and ductile shearing with normal stratigraphic sequence. The resulting structures are structural assemblage of the folding layers which occurred in extensional tectonic regime during the Late Permian-Triassic Period.