陕西旬北浅变质岩区的大型层滑构造

LARGE-SCALE BEDDING-SLIDING STRUCTURE IN XUNBEI EPIMETAMORPHIC ROCK REGION, SHAANXI

笔者着重探讨陕西旬北地区志留系和泥盆系浅变质岩的构造特征，发现这两套地层在构造式样上有明显的差异，它们之间存在着大型的顺层滑动构造─－层滑构造，层滑构造面上下的两套地层是相对独立的构造变形单元。通过对层滑构造的进一步研究，得出区域面理的形成与层滑构造有密切成因联系的新认识。浅变质岩区岩性较柔软的岩层常常发生大面积的面理置换作用，这种面理是大型层滑构造和岩石圈内部多层次滑脱拆离体系的伴生构造，属超大型Ｓ型面理。

An emphatic approach is made in this paper to the structural characteristics of Silurian and Devonian epimetamorphic rocks in Xunbei district of Shaanxi Province. The study shows that there is an obvious difference between the structural patterns of the strata of Silurian and Devonian Systems and reveals the presence of a large bedding-sliding structure. Its structural plane separates the strata as two relative independent units of structural deformation. The further study on the bedding-sliding structure gains a new understanding for the regional foliation formation closely linked in its genesis to the bed-sliding structure. The regional foliation, which occurred often and widely in the relative soft rockbed of the epimetamorphic rocks due to the foliation replacement, is a kind of associated structure of the largescale bedding-sliding structure and the decollement-breakaway systems in different levels within the lithosphere, and belongs to supperlarge scale S-type foliation.