福庆寺剪切带剪切指向标志及剪切方向的确定

福庆寺剪切带中宏观发育S-C面状构造,不对称的透镜状构造(或眼球),由变形变质分异而形成的无根石英脉的不对称状“布丁”等明显可辨的剪切指向标志;显微的糜棱面理(Sm)及剪切条带(Shear bands)、云母的掀斜现象、黄铁矿晶体的压力影、显微破裂等是剪切指向标志在显微域中的表现;糜棱岩中石英光轴组构的不对称性也提供了揭示剪切带运动特点的佐证。刘剪切带线状构造的分类统计,获得该剪切带在韧性变形阶段,a线理(矿物拉伸线理、原生气孔杏仁的拉伸方向)以中—高角度向NE侧状,反映了此阶段剪切带发生了逆冲—左行斜冲剪切运动,在脆性变形阶段,擦痕线理以高角度向SW侧状,则指示了该剪切带在后期活动阶段的高角度右行斜冲剪切运动性质。

Determination of Shear Criteria and Sense in the Fuqingsi Shear Zones, Jingxing, Hebei

The features of shear criteria in the Fuqingshi shear zones, developed in the Lower -Preterozoic lightly metamorphic arkoses- conglomerates and andesites above the conformarity between the Preterozoic and the Archean with NW-dip in a middle angle, are shown in this paper. They are S-C foliation structures, assymetric lenticles (augeus), assymetric boudins of rootless quartz veins and so on in macroscale and mylonitic schistosities or-shear bands, domino structures, pressure shadows, micro- fractures etc. in micro-scale. Assymetry of preferred orientation pattem of quartz C-axes-in phyllonites of the shear zones is also better evidence for determing the shear sense,. Inverstigation for lineations of the shear zones show that a-lineation (stretching mineral lineation, stretching primary fumaroles and amygdales) plunges north in a middle-higher angle at the ductile deformation stage, and that the lineation of striation plunges west in a higher angle at the brittle deformation stage. Syntheses of above data indicates that the Fuqingshe shear zones underwent sinistrally shearing with NW-side up during the ductile deformation and dextralmmovement with NW-side up during the brittle deformation, respectively.