海南岛小妹韧性剪切带的纳米尺度
Xiaomei Ductile Shear Zone on Hainan Island in a Nanoscale Perspective

为查明构造性质不明、空间位置不清楚的南海北缘琼南缝合带西段——九所-陵水断裂带，采集断裂带东段小妹韧性剪切带中花岗岩、石榴石石英片岩和花岗质片麻岩3类样品，探讨其纳米尺度特征.扫描电镜(scanning electron microscope，SEM)观测结果表明：这3类岩石存在多种纳米结构和构造，结合野外实践得到的该剪切带纳米颗粒的发育程度与其所受剪切作用有关.纳米颗粒的形成机制可能有：(1)剪切力作用下层状硅酸盐热分解；(2)颗粒塑性变形后发生脆性破裂，再经剪切作用研磨而成.与台湾太鲁阁深大断裂带中的韧性剪切带岩石样品进行SEM测试结果对比，发现其纳米颗粒特征和研究区具可比性，据此推测小妹韧性剪切带在区域构造归属上可能与九所-陵水深大断裂带密切相关.
The western Qiongnan suture zone, i.e., Jiusuo-Lingshui fault belt, at the northern margin of the South China Sea, is important in tectonics. To better understand the tectonic evidences and ductile shear belts, a study is done in this area. Three types of rocks are sampled from the Xiaomei ductile shear zone on Hainan island, including granite, garnet quartz schist and granitic gneiss. Their shear surfaces were observed and analyzed through scanning electron microscope (SEM) at nanoscale. The results show multiple nano-textures and nanostructures in all three kinds of rocks and a positive relationship between the development degree of nanoparticles and the stress of the rocks. The authors propose several possible formation machanism of nanoparticles on the shear surfaces in this area, which may be thermal decomposition of sheet silicates under shear stress, or brittle deformation of minerals (especially feldspar with mechanical twins) after ductile deformation, then followed by crushing and grinding of the particles to nanoscale under shear force. Samples from the Taroko ductile shear belt, a part of the Taroko fault zone in Taiwan show similar nano characteristics to the Xiaomei ductile shear zone, implying both may have been in the same tectonic setting of a deep fracture as the Jiusuo-Lingshui fault belt. This study can therefore provide important observational facts for determining the structural properties and spatial positions of the Jiusuo-Lingshui fault belt