天目山—白际山大型剪切带南段的显微构造及变形特征

RESEARCH ON MICROSTRUCTURE AND DEFORMATION IN THE SOUTHERN SEGMENT OF THE TIANMUSHAN—BAIJISHAN MAJOR SHEAR ZONE

天日山—白际山大型左旋走向滑动剪切带南段为一韧性、脆—韧性剪切带。该带的L—S型变形组构和构造岩呈有规律的带状分布,其线应变及剪应变呈不均匀简单剪切特征。在其不同层位上,因变形环境及变形机制不同,故剪切类型也不同。文末建立的地壳内大型走向滑动剪切带的垂深模式能够反映上述特征。

In the southern segment of the Tianmushan-Bajishan major shearzone, ductile shear zone and brittle-ductile shear zone are now exposedat erosion levels which correspond respective to deeper and middle levelswhen the major shear zone was active in the Indosinian period. The shearzones were subject to brittle fracturing at higher level in the Yenshanperiod. By the measures of strain using Rf/φ method (Dunnet, 1969) andcentre to centre method (Ramsay, 1967) in this zone, the strain field inthe southern segment of the major shear zone is established. It suggeststhat linear and shear strain decreases from the centre to the edge of thiszone. The shear zone in the deeper level displays larger linear strain.The calculation of the Flinn parameter proves the shear zone developedunder the simple shearing. The temperature increased 155.2 by shear hea-ting in the centre of this zone. Value of differential stress was biggestin the centre, up to 801b. Deforming conditions and mechanisms in thethree types of the shear zone were different.