Radiative thermal conductivity of single-crystal bridgmanite at the core-mantle boundary with implications for thermal evolution of the Earth
Radiative thermal conductivity of single-crystal bridgmanite at the core-mantle boundary with implications for thermal evolution of the Earth
复制标题
核幔边界处单晶桥锰矿的辐射热导率对地球热演化的影响
DOI：
10.1016/j.epsl.2021.117329
复制
发表时间：
2022
影响因子：
5.3
通讯作者：
Holtgrewe Nicholas
中科院分区：
文献类型：
--
作者：
Murakami Motohiko;Goncharov Alexander F.;Miyajima Nobuyoshi;Yamazaki Daisuke;Holtgrewe Nicholas
自形成以来，地球一直从地球内部深处向地表释放大量热量，这主要驱动地幔对流和许多构造活动。在这个热传输过程中，热熔融核与固态地幔矿物直接接触的核幔边界对于将核热能传递到上覆地幔发挥了重要作用。尽管人们认为最下地幔的主要传热机制是主要的最下地幔矿物桥锰石的传导和辐射，但桥锰石的辐射导热性迄今为止还没有受到很好的限制。在这里，我们基于新建立的单晶桥锰矿在相应深部下地幔条件下原位进行的光吸收测量，揭示了核幔边界处桥锰矿的辐射热导率相当高，接近~5.3±1.2 W/mK。我们发现核心-地幔边界处的整体热导率比传统假设值高约1.5倍，这支持了来自核心的更高的热流，因此地幔对流比预期更剧烈。结果表明，地幔的冷却效率要高得多，这最终会削弱由地幔对流驱动的许多构造活动，其速度比传统认为的热传导行为预期的要快。
The Earth has been releasing vast amounts of heat from deep Earth's interior to the surface since its formation, which primarily drives mantle convection and a number of tectonic activities. In this heat transport process the core-mantle boundary where hot molten core is in direct contact with solid-state mantle minerals has played an essential role to transfer thermal energies of the core to the overlying mantle. Although the dominant heat transfer mechanisms at the lowermost mantle is believed to be both conduction and radiation of the primary lowermost mantle mineral, bridgmanite, the radiative thermal conductivity of bridgmanite has so far been poorly constrained. Here we revealed the radiative thermal conductivity of bridgmanite at core-mantle boundary is substantially high approaching to ∼5.3±1.2 W/mK based on newly established optical absorption measurement of single-crystal bridgmanite performedin-situunder corresponding deep lower mantle conditions. We found the bulk thermal conductivity at core-mantle boundary becomes ∼1.5 times higher than the conventionally assumed value, which supports higher heat flow from core, hence more vigorous mantle convection than expected. Results suggest the mantle is much more efficiently cooled, which would ultimately weaken many tectonic activities driven by the mantle convection more rapidly than expected from conventionally believed thermal conduction behavior.