Azuma Shintaro, Katayama Ikuo, Nakakuki Tomoeki
Department of Earth and Planetary Systems Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan.
Sci Rep. 2014 Mar 18;4:4403. doi: 10.1038/srep04403.
Plate tectonics is largely responsible for material and heat circulation in Earth, but for unknown reasons it does not exist on Venus. The strength of planetary materials is a key control on plate tectonics because physical properties, such as temperature, pressure, stress, and chemical composition, result in strong rheological layering and convection in planetary interiors. Our deformation experiments show that crustal plagioclase is much weaker than mantle olivine at conditions corresponding to the Moho in Venus. Consequently, this strength contrast may produce a mechanical decoupling between the Venusian crust and interior mantle convection. One-dimensional numerical modeling using our experimental data confirms that this large strength contrast at the Moho impedes the surface motion of the Venusian crust and, as such, is an important factor in explaining the absence of plate tectonics on Venus.
板块构造在很大程度上负责地球内部的物质和热量循环，但出于未知原因，金星上不存在板块构造。行星物质的强度是板块构造的关键控制因素，因为诸如温度、压力、应力和化学成分等物理性质会导致行星内部出现强烈的流变分层和对流。我们的变形实验表明，在与金星莫霍面相对应的条件下，地壳斜长石比地幔橄榄石弱得多。因此，这种强度差异可能导致金星地壳与内部地幔对流之间产生机械解耦。利用我们的实验数据进行的一维数值模拟证实，莫霍面处的这种巨大强度差异阻碍了金星地壳的表面运动，因此是解释金星上不存在板块构造的一个重要因素。
