Z字型叠加褶皱

THE Z-SHAPED SUPERPOSED FOLDS IN PRECAMBRIAN EAST QINLING METAMORPHIC SUITES

在东秦岭前寒武系变质岩中,发育了许多Z字型叠加褶皱。它们是由近直立的片麻岩和长英质脉形成的。不同于兰姆赛分类中的叠加褶皱。本文主要讨论它的形成条件、形态特征和叠加样式。

Z-shaped superposed folds formed by nearly vertical gneiss and feldspar-quartz veins are widely developed in East Qinling Precam-brian metamorphic rocks. Their main characteristics are: S^1 is cross-cut or replaced by S_(34)Z-shape with a short middle wing and twolong side wings. According to the relationship between schistosity S_1 and stress axes. and the angle between midwing and side wings.thesuperposed folds can be classified into two categories(a.b) and five types(a_1.1,a_1.2). The mechanism of formation of the Z-shaped super-posed folds coincides with the regional strutural development clearly illustrating the three deformations in the East Qinling district. D_1is characterized in compression from NE to SW, D_2 is compression and clockwise twisting from NW to SE. D_3 is another a strong NE-SW compression.