加拿大不列颠哥伦比亚大学Smit, Matthijs A.研究团队报道了全球热点熔岩的常见前体。相关论文发表在2024年9月19日出版的《自然—地球科学》杂志上。

据介绍，热点熔岩表现出化学非均质性，其主要原因是地幔深部岩浆的非均质性，地幔深部岩浆中含有不同成分，其组成、起源和年龄各不相同。然而，直接表征原始熔体成分和地幔非均质性是具有挑战性的。

该团队研究了热点熔岩的全球数据集，以限制其母熔体和岩石的不相容元素组成。微量元素比值表明，全球热点熔岩的成分不均匀性不是主要的，而是反映了热点熔岩上升到地表所经历的过程。

研究人员发现，这些熔岩的母熔体以及来自大火成岩省的金伯利岩和玄武岩的母熔体，在元素、放射性成因和稀有气体同位素组成上是一致的。

研究人员认为所有这些熔岩的母熔体都来自于一个枯竭和失气的地幔储层，该储层在太古宙期间被不相容的富元素物质补充。这种说法解释了热点熔岩的元素、放射性成因和惰性气体同位素组成，而不需要非均质下地幔或原始地球未脱气遗迹的长期存在。

附：英文原文

Title: A common precursor for global hotspot lavas

Author: Smit, Matthijs A., Kooijman, Ellen

Issue&Volume: 2024-09-19

Abstract: Hotspot lavas exhibit chemical heterogeneity, much of which is ascribed to heterogeneous deep mantle sources that contain various components with distinct composition, origin and age. However, characterizing primary melt compositions and mantle heterogeneity directly is challenging. Here we investigate a global dataset of hotspot lavas to constrain the incompatible-element composition of their parental melts and sources. Trace-element ratios indicate that the compositional heterogeneity of global hotspot lavas is not primary, but reflects processes that hotspot melts undergo as they ascend to the surface. We find the parental melts of these lavas, as well as of kimberlites and basalts from large igneous provinces, to be uniform in their elemental, and radiogenic and noble-gas isotope, composition. We suggest that the parental melts to all of these lavas derive from a depleted and outgassed mantle reservoir that was replenished with incompatible element-enriched material during the Archaean. This interpretation explains the elemental, radiogenic and noble-gas isotope compositions of hotspot lavas without requiring a heterogeneous lower mantle or the long-term survival of undegassed relics from a primordial Earth.

DOI: 10.1038/s41561-024-01538-7

Source: https://www.nature.com/articles/s41561-024-01538-7