Al Asad Manar, Lau Harriet C P
Department of Earth, Environmental, and Planetary Sciences, Brown University, 324 Brook St., Providence, RI 02912, USA.
Department of Earth & Planetary Science, University of California, Berkeley, 307 McCone Hall, Berkeley, CA 94720, USA.
Sci Adv. 2024 Aug 2;10(31):eadp1991. doi: 10.1126/sciadv.adp1991.
Conventional Earth evolution models are unable to simultaneously reproduce two fundamental observations: the mantle's secular temperature record and a long-lived geodynamo before inner core nucleation. Today, plate tectonics efficiently cools the mantle, but if assumed to operate throughout Earth's history, past mantle temperature and plate motion become unrealistically high. Through coupled core-mantle modeling that self-consistently predicts multiple mantle convection regimes, we show that over most of the Precambrian, Earth likely operated in a distinct "sluggish-lid" tectonic mode, characterized by partial decoupling between the lithosphere and mantle. This dominant early regime is due to a hotter Earth and the presence of the asthenosphere. This mode regulates the core-mantle boundary heat flow, which powers the geodynamo before inner core nucleation. Both sluggish-lid tectonics and a long-lived dynamo demonstrate the inextricably connected paths of the core-mantle system. Moreover, our simulations simultaneously satisfy diverse geological observations and are consistent with emerging interpretations of such records.
地幔的长期温度记录以及内核成核之前的长期地球发电机活动。如今，板块构造有效地冷却了地幔，但如果假设其在地球历史上一直运行，过去的地幔温度和板块运动会变得高得不切实际。通过自洽地预测多种地幔对流状态的地核-地幔耦合模型，我们表明在前寒武纪的大部分时间里，地球可能以一种独特的“滞流盖层”构造模式运行，其特征是岩石圈和地幔之间存在部分解耦。这种早期的主导模式是由于地球更热以及软流圈的存在。这种模式调节了地核-地幔边界的热流，为内核成核之前的地球发电机提供动力。滞流盖层构造和长期的发电机活动都表明了地核-地幔系统的紧密相连的路径。此外，我们的模拟同时满足了各种地质观测结果，并且与这些记录的新解释一致。
