Development of a new paleopiezometer based on deformation microstructures : application to mantle flow

对暴露良好的阿曼蛇绿岩Hilti地幔剖面的结构和组构分析表明，剪切带的发育可能是洋板碎裂的结果，受古海脊原有地幔组构的影响。在地幔剖面的详细构造填图显示了一个东西向流动的缓缓起伏的结构。一条NW-SE走滑剪切带横穿该水平构造。面理中橄榄石的晶体择优取向(CPO)以(010)轴向为主，而不是更常见的(010)[100]轴向，表明莫霍面附近的水平流动为非同轴流。低温剪切带内的橄榄石CPO具有(001)[100]花样和左旋剪切意义。洋地幔岩石圈在俯冲和俯冲过程中的结构行为可能受到大洋扩张中心形成的初始力学各向异性的强烈影响。

Structural and fabric analysis of the well-exposed Hilti mantle section, Oman ophiolite, suggests that shear zone development, which may have resulted from oceanic plate fragmentation, was influenced by pre-existing mantle fabric present at the paleo-ridge. Detailed structural mapping in the mantle section revealed a gently undulating structure with an east-west flow direction. A NW-SE strike-slip shear zone cuts across this horizontal structure. The crystal preferred orientation (CPO) of olivine within the foliation is dominated by (010) axial patterns rather than more commonly observed (010) [100] patterns, suggesting that the horizontal flow close to the Moho involved non-coaxial flow. Olivine CPO within the shear zone formed at low temperature is characterized by (001) [100] patterns and a sinistral sense of shear. The structural behavior of oceanic mantle lithosphere during subduction and obduction may be strongly influenced by initial mechanical anisotropy developed at an oceanic spreading center.