Potassium and uranium in the upper mantle controlled by Archean oceanic crust recycling
Potassium and uranium in the upper mantle controlled by Archean oceanic crust recycling
复制标题
太古代洋壳循环控制的上地幔钾和铀
作者：
Nielsen S
地球的地幔被分成不同的储层。从今天喷发的玄武岩熔岩中，我们知道上地幔缺乏不相容的微量元素，而洋岛玄武岩（OIB）则是一个更深、更富集的储层。在上地幔和下地幔岩浆中，钾（K）和铀（U）这两种不相容元素表现出不同的比值。这是令人惊讶的，因为它们在地幔熔融期间基本上不断裂，因此在地球历史上从上地幔连续提取熔体不能解释这种差异。在这里，构建一个模型，其中U是不溶的大陆风化在缺氧条件下的早期地球。这导致了地球早期高K/U的洋壳再循环，而在显著的氧化风化开始后，则是低K/U。2200毫安这一概念再现了在上地幔和下地幔储层以及大陆地壳中观察到的K/U。该模型还示出占钍/铀比，从而铅（铅）同位素组成在这些水库。成功的模型解意味着：（1）地球早期海洋的化学风化通量明显高于今天，（2）大部分OIB储层的年龄小于2200 Ma。
The Earth's mantle is divided into separate reservoirs. From basaltic lavas erupted today we know that the upper mantle is depleted in incompatible trace elements, whereas ocean island basalts (OIB) sample a deep, more enriched reservoir. The two incompatible elements potassium (K) and uranium (U) display a different ratio to each other in lavas from the upper and lower mantle reservoirs. This is surprising because they do not fractionate substantially during melting of the mantle and therefore continuous extraction of melts from the upper mantle over Earth's history cannot explain this disparity. Here a model is constructed in which U is insoluble during continental weathering in the anoxic conditions of the early Earth. This leads to recycling of oceanic crust with high K/U in the early Earth and low K/U after significant oxidative weathering commenced ca. 2200 Ma. This concept reproduces the observed K/U in both the upper and lower mantle reservoirs as well as the continental crust. The model is also shown to account for the thorium/uranium ratios and thereby Pb (lead) isotope compositions in these reservoirs. Successful model solutions imply that (1) chemical weathering fluxes to the oceans on the early Earth were significantly higher than present day, and (2) that the majority of the OIB reservoir is younger than 2200 Ma.
大陆地壳 232Th/238U 比值 (κ) 的约束
影响因子：
3.7
作者：
Debajyoti Paul;William M. White;Donald L. Turcotte
通讯作者：
Donald L. Turcotte
回收的洋壳在地球钾和氩预算中的作用：解决“氩缺失”问题
DOI：
--
发表时间：
2004
期刊：
影响因子：
--
作者：
J. C. Lassiter
通讯作者：
J. C. Lassiter
影响因子：
5.3
作者：
Schmidt, MW;Poli, S
通讯作者：
Poli, S