Sulphur isotopes of alkaline magmas unlock long-term records of crustal recycling on Earth
Sulphur isotopes of alkaline magmas unlock long-term records of crustal recycling on Earth
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DOI：
10.1038/s41467-019-12218-1
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发表时间：
2019-09
影响因子：
16.6
通讯作者：
W. Hutchison;Rainer J. Babiel;A. Finch;M. Marks;G. Markl;A. Boyce;E. Stüeken;H. Friis;A. Borst;N. Horsburgh
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文献类型：
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作者：
W. Hutchison;Rainer J. Babiel;A. Finch;M. Marks;G. Markl;A. Boyce;E. Stüeken;H. Friis;A. Borst;N. Horsburgh
地球表面和地幔的硫储层通过俯冲、地壳再循环和火山作用连接在一起。虽然海洋热点熔岩目前对深部硫循环提供了最好的限制，但它们有限的年龄范围（<200 Ma）意味着它们无法揭示地球历史上地壳循环的时间变化。富含硫的碱性岩浆提供了解决方案，因为它们与回收的来源（即交代的岩石圈地幔和地幔柱）有关，并且至关重要的是，在整个地质记录中都可以找到。在这里，我们提出了一个详细的研究硫同位素分馏在中元古界碱性省格陵兰岛，并证明，富集俯冲影响源（δ 34 S的+1至+5‰）可以重建。全球δ 34 S汇编揭示了碱性岩浆源的长期变化，支持岩石圈地幔成分和/或深部地壳再循环的Ga时间尺度的变化。因此，碱性岩浆代表了一个强大的，但未充分利用的仓库，通过地质时间来询问地壳循环。
Earth’s surface and mantle sulphur reservoirs are connected via subduction, crustal recycling and volcanism. Although oceanic hotspot lavas currently provide the best constraints on the deep sulphur cycle, their restricted age range (<200 Ma) means they cannot reveal temporal variations in crustal recycling over Earth history. Sulphur-rich alkaline magmas offer the solution because they are associated with recycled sources (i.e. metasomatized lithospheric mantle and plumes) and, crucially, are found throughout the geological record. Here, we present a detailed study of sulphur isotope fractionation in a Mesoproterozoic alkaline province in Greenland and demonstrate that an enriched subduction-influenced source (δ34S of +1 to +5‰)can be reconstructed. A global δ34S compilation reveals secular variation in alkaline magma sources which support changes in the composition of the lithospheric mantle and/or Ga timescales for deep crustal recycling. Thus, alkaline magmas represent a powerful yet underutilized repository for interrogating crustal recycling through geological time.