Extensive crustal extraction in Earth’s early history inferred from molybdenum isotopes
Extensive crustal extraction in Earth’s early history inferred from molybdenum isotopes
复制标题
DOI：
10.1038/s41561-019-0451-2
复制
发表时间：
2019-09
影响因子：
18.3
通讯作者：
A. McCoy-West;P. Chowdhury;K. Burton;P. Sossi;G. Nowell;J. Fitton;A. Kerr;Peter A. Cawood;H. Williams
中科院分区：
文献类型：
--
作者：
A. McCoy-West;P. Chowdhury;K. Burton;P. Sossi;G. Nowell;J. Fitton;A. Kerr;Peter A. Cawood;H. Williams
根据锆石年龄和放射性同位素对最早地壳体积的估计仍然不明确。稳定的同位素系统，如钼，有可能提供进一步的制约，但由于地幔和地壳储藏之间缺乏互补性，仍未得到充分利用。文中给出了太古代科马提岩和显生宙科马提岩和苦苦岩的钼同位素数据，并论证了它们的地幔来源都具有与上球粒体陆壳互补的软骨下特征。这些结果证实了现今地幔的枯竭程度是在35亿年前达到的，地球在钼的再循环方面一直处于稳定状态。物质平衡模拟表明，这种早期的地幔枯竭需要开采出比之前认为的更大的以镁铁质为主的原壳，是今天大陆地壳体积的两倍多，这意味着在地球历史的头10亿年里，地壳迅速增长和破坏。
Estimates of the volume of the earliest crust based on zircon ages and radiogenic isotopes remain equivocal. Stable isotope systems, such as molybdenum, have the potential to provide further constraints but remain underused due to the lack of complementarity between mantle and crustal reservoirs. Here we present molybdenum isotope data for Archaean komatiites and Phanerozoic komatiites and picrites and demonstrate that their mantle sources all possess subchondritic signatures complementary to the superchondritic continental crust. These results confirm that the present-day degree of mantle depletion was achieved by 3.5 billion years ago and that Earth has been in a steady state with respect to molybdenum recycling. Mass balance modelling shows that this early mantle depletion requires the extraction of a far greater volume of mafic-dominated protocrust than previously thought, more than twice the volume of the continental crust today, implying rapid crustal growth and destruction in the first billion years of Earth’s history.