Giuliani Andrea, Pearson D Graham, Soltys Ashton, Dalton Hayden, Phillips David, Foley Stephen F, Lim Emilie, Goemann Karsten, Griffin William L, Mitchell Roger H
KiDs (Kimberlites and Diamonds), School of Earth Sciences, The University of Melbourne, Parkville, 3010 Victoria, Australia.
Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS) and GEMOC, Department of Earth and Planetary Sciences, Macquarie University, North Ryde, 2109 New South Wales, Australia.
Sci Adv. 2020 Apr 24;6(17):eaaz0424. doi: 10.1126/sciadv.aaz0424. eCollection 2020 Apr.
Quantifying the compositional evolution of mantle-derived melts from source to surface is fundamental for constraining the nature of primary melts and deep Earth composition. Despite abundant evidence for interaction between carbonate-rich melts, including diamondiferous kimberlites, and mantle wall rocks en route to surface, the effects of this interaction on melt compositions are poorly constrained. Here, we demonstrate a robust linear correlation between the Mg/Si ratios of kimberlites and their entrained mantle components and between Mg/Fe ratios of mantle-derived olivine cores and magmatic olivine rims in kimberlites worldwide. Combined with numerical modeling, these findings indicate that kimberlite melts with highly variable composition were broadly similar before lithosphere assimilation. This implies that kimberlites worldwide originated by partial melting of compositionally similar convective mantle sources under comparable physical conditions. We conclude that mantle assimilation markedly alters the major element composition of carbonate-rich melts and is a major process in the evolution of mantle-derived magmas.
量化地幔衍生熔体从源区到地表的成分演化对于限制原生熔体的性质和深部地球成分至关重要。尽管有大量证据表明富含碳酸盐的熔体（包括含金刚石的金伯利岩）与地幔围岩在到达地表的途中存在相互作用，但这种相互作用对熔体成分的影响仍缺乏严格限制。在此，我们展示了全球范围内金伯利岩的Mg/Si比值与其夹带的地幔组分之间以及金伯利岩中地幔衍生橄榄石核与岩浆橄榄石边缘的Mg/Fe比值之间存在稳健的线性相关性。结合数值模拟，这些发现表明，在岩石圈同化之前，成分高度可变的金伯利岩熔体大致相似。这意味着全球的金伯利岩是在可比的物理条件下由成分相似的对流地幔源区部分熔融形成的。我们得出结论，地幔同化显著改变了富含碳酸盐熔体的主要元素组成，并且是地幔衍生岩浆演化的一个主要过程。
