金星非单调冷却热演化历史分析

Analysis of the non-monotony cooling on the thermal evolution history of Venus

金星表层年龄和构造活动特点表明其岩石层在最近的地质历史时期经历过广泛的更新.这种全球性的表层改造与其内部热演化历史进程密切相关.如果金星存在相变形成的上、下地幔,依据现今所了解的金星物理性质和参量化的热对流理论,并且考虑金星地幔相变边界层状态对对流的控制作用,我们计算了金星热演化历史.结果表明,金星的热演化历史是一种非单调的冷却过程,在这种非单调的热演化历史进程中,金星地幔会出现大体等周期的翻转.由于参数选取的不同,翻转时金星上、下地幔的温差随时间可能出现稳定变化、逐渐加强、逐渐减弱三种不同演化模式,目前尚不能确定实际金星热演化历史究竟是哪一种模式.金星地幔相变边界层的穿透对流可能是推动其表层岩石层全球性更新的关键,导致其表层火山活动和地表构造以大致500 Ma时间间隔更新和重造.

Venus＇ mean surface age suggests that there may have extensive resurfacing of Venus prior to that epoch. Such global resurfacing is relative with the thermal evolution in the interior. Base on the properties and parameters of the Venus and the theory of mantle convection, we calculate the thermal evolution history of Venus. The results show that Venus＇ thermal evolution is a non-monotonic cooling process. In this process, Venus＇ mantle convection displays an overturn with a quasi-periodicity. Because of the different parameters, the stales of mantle overturn may appear in three modes. The punctuated turn over and avalanche effect in phase transition layer may play a key role for the resurfacing and lithosphere foundered of Venus in 500 Ma intervals.