米仓山变质带火地垭群中片内无根褶皱与面理置换

片内无根褶皱是变质岩系中分布广泛的一种小型构造,它的存在是面理置换的重要判据之一(特纳等,1963),对于认识区域性面理的成因,恢复区域构造具有重要意义。本文对四川北部南江上两地区火地垭群中片内无根褶皱进行了研究。

ROOTLESS INTRAFOLIAL FOLDS AND FOLIATION TRANSPOSITION IN THE HUODIYA GROUP IN THE METAMORPHIC ZONE OF MOUNT MICANG

In the metamorphic zone of Mount Micang in the north Sichuan Province, rootless in-trafolial folds are rather well developed in the Huodiya Group of Presinian. According to the mode of genesis, they can be classified into four basic types: tension fracture, shear-fracture, stick-slip and compression. In general, they are associated to form various assemblages. The rootless intrafolial folds were formed in rock strata with an alternation of competent and imcompetent beds due to the flattening by persistent compression. From the study of the rootless intrafolial folds and regional geological structures, we conclude that the regional schistosity of the Huodiya Group is not a bedding schistosity, but an axial-plane schi-stosity(S₁), which has entirely transposed the primary stratification(S₀).