The interaction between the post-perovskite phase change and a thermo-chemical boundary layer near the core-mantle boundary
The interaction between the post-perovskite phase change and a thermo-chemical boundary layer near the core-mantle boundary
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DOI：
10.1016/j.epsl.2005.06.048
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发表时间：
2005-09
影响因子：
5.3
通讯作者：
T. Nakagawa;P. Tackley
中科院分区：
文献类型：
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作者：
T. Nakagawa;P. Tackley
利用新发现的后钙钛矿(PPV)相变对热化学地幔对流进行了数值模拟，以表征其对D“区的动力学后果，D”区通常被解释为起源于热化学。PPV区的外观存在很强的横向变化，CMB温度较高，导致在平均或冷区相界“双交叉”，或在热区不相交。较低的CMB温度导致到处都是单一的交叉，但深度变化很大。后钙钛矿相变的强烈放热性质导致了包含厚PPV层的区域与从俯冲板块分离的地壳成分形成的化学致密物质堆之间的反相关。PPV相变破坏了化学致密物质的稳定，使俯冲的板片很容易渗透到致密层中，形成后钙钛矿相的孤立斑块。地幔深部热异常的横向谱以长波为主，而成分的横向谱相对平坦，是除最长波以外所有波长地震速度变化的主要贡献者。
Numerical simulations of thermo-chemical mantle convection with the newly-discovered post-perovskite (PPV) phase change are used to characterize its dynamical consequences for the D” region, which has frequently been interpreted as being thermo-chemical in origin. A strong lateral variation in the appearance of the PPV region is observed, with high CMB temperatures leading to “double-crossing” of the phase boundary in average or cold regions, or no crossing in hot regions. Lower CMB temperatures result in a single crossing everywhere but with highly variable depth. The strongly exothermic nature of the post-perovskite phase change induces an anti-correlation between regions containing a thick PPV layer and piles of chemically dense material formed by the segregation of the crustal component from subducted slabs. The PPV phase change destabilizes chemically-dense material, allowing subducted slabs to easily penetrate into a dense layer, forming isolated patches of the post-perovskite phase. Whereas the lateral spectrum of thermal anomalies in the deep mantle is dominated by long wavelengths, the lateral spectrum of composition is relatively flat and is the dominant contributor to seismic velocity variations at all wavelengths except the very longest ones.