Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory 0200, Australia.
Nature. 2012 Nov 29;491(7426):698-704. doi: 10.1038/nature11678.
The magmatic layers of the oceanic crust are created at constructive plate margins by partial melting of the mantle as it wells up. The chemistry of ocean floor basalts, the most accessible product of this magmatism, is studied for the insights it yields into the compositional heterogeneity of the mantle and its thermal structure. However, before eruption, parental magma compositions are modified at crustal pressures by a process that has usually been assumed to be fractional crystallization. Here we show that the global distributions of trace elements in ocean floor basalts describe a systematic pattern that cannot be explained by simple fractional crystallization alone, but is due to cycling of magma through the global ensemble of magma chambers. Variability in both major and incompatible trace-element contents about the average global pattern is due to fluctuations in the magma fluxes into and out of the chambers, and their depth, as well as to differences in the composition of the parental magmas.
大洋地壳的岩浆层是在地壳的建设性板块边缘由地幔的部分熔融形成的，而地幔则是向上涌升的。海底玄武岩是这种岩浆作用的最易接近的产物，其化学性质被研究，以了解地幔的成分非均质性及其热结构。然而，在喷发之前，原始岩浆的成分在地壳压力下通过一个通常被认为是分馏结晶的过程发生改变。在这里，我们表明，大洋海底玄武岩中微量元素的全球分布描述了一种系统的模式，不能仅用简单的分馏结晶来解释，而是由于岩浆在全球岩浆室集合中循环所致。关于全球平均模式的主要和不相容微量元素含量的变化是由于进入和离开这些室的岩浆通量及其深度的波动以及母岩浆的组成差异所致。
