Initiation of plate tectonics in the Hadean: Eclogitization triggered by the ABEL Bombardment
Initiation of plate tectonics in the Hadean: Eclogitization triggered by the ABEL Bombardment
复制标题
DOI：
10.1016/j.gsf.2016.11.009
复制
发表时间：
2016-12
影响因子：
8.9
通讯作者：
S. Maruyama;M. Santosh;S. Azuma
中科院分区：
文献类型：
--
作者：
S. Maruyama;M. Santosh;S. Azuma
板块构造何时在地球上开始一直是争论不休的话题，在这里，我们讨论这个话题的基础上，地月地质和小行星带的记录，得出结论，板块构造的开始是在中东Hadean（4.37-4.20 Ga）。板块构造的触发是ABEL轰击，它将海洋和大气成分输送到完全干燥的还原地球上，最初由顽火辉石类物质组成。通过挥发分的吸积作用，撞击部位CI球粒陨石和表壳岩同时发生了冲击变质作用，并在潮湿条件下发生了显著的重结晶作用，在由21 km厚的斜长岩组成的长英质上地壳和50 km甚至更厚的KREEP下地壳组成的原始大陆中产生了大量的榴辉岩化作用。榴辉岩化作用一定产生了强大的板块拉力，从而在冥古宙中期启动了板块构造。另一个重要因素是轰炸的规模。通过在撞击物上创造1000公里的太平洋级撞击坑，自早冥古宙以来运作停滞盖构造的刚性板块被严重破坏，海洋岩石圈在地球上产生了双峰岩石圈，使板块构造得以运作。考虑到ABEL轰击事件的重要性，我们认为，Hadean Eon可以分为三个阶段：（1）早Hadean（4.57-4.37 Ga），（2）中Hadean（4.37-4.20 Ga），（3）晚Hadean（4.20-4.00 Ga）。
When plate tectonics began on the Earth has been long debated and here we argue this topic based on the records of Earth-Moon geology and asteroid belt to conclude that the onset of plate tectonics was during the middle Hadean (4.37–4.20 Ga). The trigger of the initiation of plate tectonics is the ABEL Bombardment, which delivered oceanic and atmospheric components on a completely dry reductive Earth, originally comprised of enstatite chondrite-like materials. Through the accretion of volatiles, shock metamorphism processed with vaporization of both CI chondrite and supracrustal rocks at the bombarded location, and significant recrystallization went through under wet conditions, caused considerable eclogitization in the primordial continents composed of felsic upper crust of 21 km thick anorthosite, and 50 km or even thicker KREEP lower crust. Eclogitization must have yielded a powerful slab-pull force to initiate plate tectonics in the middle Hadean. Another important factor is the size of the bombardment. By creating Pacific Ocean class crater by 1000 km across impactor, rigid plate operating stagnant lid tectonics since the early Hadean was severely destroyed, and oceanic lithosphere was generated to have bi-modal lithosphere on the Earth to enable the operation of plate tectonics. Considering the importance of the ABEL Bombardment event which initiated plate tectonics including the appearance of ocean and atmosphere, we propose that the Hadean Eon can be subdivided into three periods: (1) early Hadean (4.57–4.37 Ga), (2) middle Hadean (4.37–4.20 Ga), and (3) late Hadean (4.20–4.00 Ga).