Boninite-like intraplate magmas from Manihiki Plateau require ultra-depleted and enriched source components.
Boninite-like intraplate magmas from Manihiki Plateau require ultra-depleted and enriched source components.
复制标题
DOI：
10.1038/ncomms14322
复制
发表时间：
2017-02-09
影响因子：
16.6
通讯作者：
Turner S
中科院分区：
文献类型：
--
作者：
Golowin R;Portnyagin M;Hoernle K;Hauff F;Gurenko A;Garbe-Schönberg D;Werner R;Turner S
Ontong Java和Manihiki海洋高原被认为是通过地幔柱头的高度熔融形成的。然而，与Ontong Java基底熔岩相比，Manihiki的玻安岩样低Ti基底岩石意味着更复杂的岩浆成因，Ontong Java基底熔岩可由原始地幔源熔融约30%产生。在这里，我们表明，微量元素和同位素组成的低钛Manihiki岩石可以最好地解释了重熔的超贫化源（可能是一个共同的地幔成分在Ontong Java和Manihiki羽源）再富集≤1%的洋-岛-玄武岩样熔体成分。不同于玻安岩形成的耐火地幔在俯冲带的水通量熔融，这些玻安岩类板内岩石形成的耐火羽状物质，已被交代的洋-岛-玄武岩类熔体通过绝热减压熔融。我们的研究结果表明，在假设所有的大洋玻安岩形成与俯冲过程之前，需要谨慎。大的火成岩省可能很快形成，但成分往往不同。在这里，作者发现Manihiki的玻安岩类岩石是超贫化源再熔融的结果，因此对地球上所有玻安岩类岩石必须与俯冲过程有关提出了质疑。
The Ontong Java and Manihiki oceanic plateaus are believed to have formed through high-degree melting of a mantle plume head. Boninite-like, low-Ti basement rocks at Manihiki, however, imply a more complex magma genesis compared with Ontong Java basement lavas that can be generated by ∼30% melting of a primitive mantle source. Here we show that the trace element and isotope compositions of low-Ti Manihiki rocks can best be explained by re-melting of an ultra-depleted source (possibly a common mantle component in the Ontong Java and Manihiki plume sources) re-enriched by ≤1% of an ocean-island-basalt-like melt component. Unlike boninites formed via hydrous flux melting of refractory mantle at subduction zones, these boninite-like intraplate rocks formed through adiabatic decompression melting of refractory plume material that has been metasomatized by ocean-island-basalt-like melts. Our results suggest that caution is required before assuming all Archaean boninites were formed in association with subduction processes. Large igneous provinces may form very quickly, but compositions often differ. Here, the authors find that boninite-like rocks at Manihiki are a result of re-melting of an ultra-depleted source therefore putting into question that all boninitic rocks on Earth must be related to subduction processes.