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

对阿曼蛇绿岩Hilti地幔剖面的构造和组构分析表明，剪切带的发育可能是由大洋板块碎裂引起的，受古脊处原有地幔组构的影响。在地幔剖面上进行详细的构造映射，揭示了一个东西向的平缓起伏构造。NW-SE走滑剪切带横贯该水平构造。橄榄石在叶理中的晶体优先取向（CPO）以（010）轴向模式为主，而不是更常见的（010）[100]模式，这表明接近莫霍的水平流动涉及非同轴流动。在低温下形成的剪切带内的橄榄石CPO具有（001）[100]模式和左旋剪切感。在俯冲和逆冲过程中，洋幔岩石圈的构造行为可能受到洋扩张中心发育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.