湖北郧县王家庄绿色纤维状石英-云母脉特征及成因--对板块构造几个问题的思考

湖北郧县王家庄有两期脉体 ,早期为纤维状石英脉 ,总体呈北北东向分布 ,平行脉壁有一中间面使其对称分布 ,显示张性裂隙持续发育过程 ;与之垂直的横向压性裂隙将它“错开”。形貌上酷似板块构造的大洋中脊和转换断层。晚期云母脉叠置在上述两组裂隙之上 ,并使原来裂隙性质发生变化。这些特征与区域应力场分布 ,特别是与两郧断裂的演化息息相关。根据分形理论 ,将王家庄石英云母脉与板块构造进行对比 ,一方面从微观的角度证实了板块构造一些基本观点的合理性。同时从微观信息得到深入研究板块构造的一些新启示 :对板块形成机制不要局限于软流圈对流 ,而应从更深层次研究地幔物质运动规律 ;要将大陆和大洋作为一个整体研究全球应力场分布规律与构造演化历史 ,其中转换断层是联系大陆和大洋的纽带 ;加强RRR型三联点研究 ,它是研究深部 (地幔 )物质运动和上部 (地壳、岩石圈 )构造应力场相互关系的重要窗口

CHARACTERISTICS AND FORMATION OF GREEN FIBROID QUARTZ-MICA VEINS AT WANGJIA VILLAGE,YUNXIAN COUNTY, HUBEI PROVINCE--SOME CONSIDERATIONS ON PLATE TECTONICS

A series of green fibroid quartz-mica veins at Wangjia Village, Yunxian County, Hubei Province show two stages of growth. At early stage appeared the fibroid quartz vein with NNE strike. There is a median surface paralleled to the vein wall in the middle of the vein. The quartz fibres are symmetrically grown from this median surface and showed a continuous development processes along the extension fracture. A series of compression fractures vertically “cut off” the fibroid quartz vein, Which is morphologically very similar to the style of transform fault cutting the oceanic ridge of the plate tectonics. These two trends of fractures are superimposed by the mica veins of the later stage. The mica veins of the later stage caused a change in the mechanical property of the fractures. The development of the fractures are closely related to the regional stress field and especially to the development of the Yunxian-Yunxi fault. In the light of fractal theory, the comparison between the green fibroid quartz-mica veins at Wangjia Village and the assemblage of the oceanic ridge-transform fault of the plate tectonics, in a small scale, proves the rationality of the basic principle of the plate tectonics. This also brings some new inspiration from microdomains to a deeper study of the plate tectonics. The stress driving plate movement seems not only to be confined to the convection of asthenosphere, but may also be caused by the mantle movement in a deeper level. Continental lithosphere and oceanic lithosphere should be regarded as a whole in studying the distribution of the global stress and the tectonic evolution. Transform fault is the link between the continental lithosphere and the oceanic lithosphere. Strengthening the study on RRR type of triple junction will open an important window for understanding the relationship between the material movement in deep level mantle and the tectonic stress field in crust or lithosphere.