A review of the isotopic and trace element evidence for mantle and crustal processes in the Hadean and Archean: Implications for the onset of plate tectonic subduction
A review of the isotopic and trace element evidence for mantle and crustal processes in the Hadean and Archean: Implications for the onset of plate tectonic subduction
复制标题
DOI：
10.1130/2008.2440(01
复制
发表时间：
2008-07
期刊：
影响因子：
--
通讯作者：
S. Shirey;B. Kamber;M. Whitehouse;P. Mueller;A. Basu
中科院分区：
文献类型：
--
作者：
S. Shirey;B. Kamber;M. Whitehouse;P. Mueller;A. Basu
相当多的地球化学证据支持在冥古宙结束后不久地球上开始了板块构造运动。在3.6 Ga时，贫化上地幔基性-超基性岩石的Nb/Th和Th/U分别从7 ~ 18.2和4.2 ~ 2.6变化。这标志着从3.9 Ga开始的俯冲开始，在总地幔环流中出现了俯冲蚀变板块。3.6 Ga以后，幼期地壳岩开始从逐渐枯竭的地幔演化而来，具有典型的火成岩ε (Nd): ε (Hf) = 1:2的特征。具有稳定的地幔龙骨并有俯冲印记的克拉通至少在3.5 Ga开始出现。这些变化都表明，从3.6 Ga开始，板块构造作用对大陆地壳的挤压逐渐耗尽了地幔。新太古代的俯冲作用在很大程度上类似于现在的俯冲作用，只是能够产生具有厚地幔龙骨的大型克拉通。最早的太古宙幼岩和冥古宙锆石的同位素组成反映了与地球增生和月球形成相关的陆相岩浆海洋中早期富集储层的分离和钙硅酸盐和镁硅酸盐钙钛矿的分选，以及随后的地壳作用叠加的综合作用。冥古宙的锆石很可能来自一个没有大陆的、基性到超基性的原地壳，在4.4 - 4.0 Ga的潮湿条件下多次重熔，产生了进化的长英质岩石。如果原地壳是由约4.4 Ga的全球地幔翻转产生的，那么向板块构造的过渡是由放射性衰变驱动的地幔加热引起的。或者，如果原地壳是由典型的地幔对流产生的，那么向板块构造的过渡是由于冷却到大型岩石圈板块稳定的程度。
Considerable geochemical evidence supports initiation of plate tectonics on Earth shortly after the end of the Hadean. Nb/Th and Th/U of mafic-ultramafic rocks from the depleted upper mantle began to change from 7 to 18.2 and 4.2 to 2.6 ( respectively) at 3.6 Ga. This signals the appearance of subduction-altered slabs in general mantle circulation from subduction initiated by 3.9 Ga. Juvenile crustal rocks began to show derivation from progressively depleted mantle with typical igneous epsilon(Nd):epsilon(Hf) = 1: 2 after 3.6 Ga. Cratons with stable mantle keels that have subduction imprints began to appear by at least 3.5 Ga. These changes all suggest that extraction of continental crust by plate tectonic processes was progressively depleting the mantle from 3.6 Ga onwards. Neo-archean subduction appears largely analogous to present subduction except in being able to produce large cratons with thick mantle keels. The earliest Eoarchean juvenile rocks and Hadean zircons have isotopic compositions that reflect the integrated effects of separation of an early enriched reservoir and fractionation of Ca-silicate and Mg-silicate perovskite from the terrestrial magma oceans associated with Earth accretion and Moon formation, superposed on subsequent crustal processes. Hadean zircons most likely were derived from a continent-absent, mafic to ultramafic protocrust that was multiply remelted between 4.4 and 4.0 Ga under wet conditions to produce evolved felsic rocks. If the protocrust was produced by global mantle overturn at ca. 4.4 Ga, then the transition to plate tectonics resulted from radioactive decay-driven mantle heating. Alternatively, if the protocrust was produced by typical mantle convection, then the transition to plate tectonics resulted from cooling to the extent that large lithospheric plates stabilized.