Pyroxenite-rich mantle formed by recycled oceanic lithosphere: Oxygen-osmium isotope evidence from Canary Island lavas
Pyroxenite-rich mantle formed by recycled oceanic lithosphere: Oxygen-osmium isotope evidence from Canary Island lavas
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DOI：
10.1130/g25613a.1
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发表时间：
2009-06
期刊：
影响因子：
5.8
通讯作者：
James M.D. Day;D. Graham Pearson;Colin G. Macpherson;D. Lowry;J. Carracedo
中科院分区：
文献类型：
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作者：
James M.D. Day;D. Graham Pearson;Colin G. Macpherson;D. Lowry;J. Carracedo
板块构造过程导致地壳和岩石圈再循环进入地幔。大洋岛玄武岩（OIB）熔岩的同位素特征表明地幔中存在长期保存的再循环储层。虽然循环成分可以解释OIB源地幔的地球化学变化，但已经表明，这些成分的直接熔融将导致岩浆的演化成分，不像OIB。相反，有人认为，无论是交代辉石丰富的橄榄岩，继承了微量元素和同位素特征的俯冲物质，或高温地幔内交代的岩石圈可以解释OIB组成。为了测试这些模型，我们提出了新的氧和锇同位素数据的火山岩从加那利群岛的耶罗岛和拉帕尔马。这些岛屿具有不同的18 O/16 O和187 Os/188 Os组成，这可以通过含有<10%再循环海洋岩石圈的富含辉石的橄榄岩地幔的熔融来解释。我们还评估了夏威夷和亚速尔群岛熔岩的O-Os同位素系统学，并表明它们也符合不同的回收海洋成分，包括岩石圈和远洋沉积物。我们的结论是，富集同位素签名的一些OIBs是一致的辉石岩丰富的地幔来源的再循环组分交代。
Plate tectonic processes result in recycling of crust and lithosphere into Earth's mantle. Evidence for long-term preservation of recycled reservoirs in the mantle comes from the enriched isotopic character of oceanic island basalt (OIB) lavas. Although recycled constituents can explain much of the geochemical variation in the OIB-source mantle, it has been shown that direct melting of these components would lead to magmas with evolved compositions, unlike OIB. Instead, it has been argued that either metasomatic pyroxene-rich peridotite that has inherited the trace element and isotopic character of subducted materials, or high-temperature intramantle metasomatism of lithosphere can explain OIB compositions. To test these models, we present new oxygen and osmium isotope data for lavas from the Canary Islands of El Hierro and La Palma. These islands have distinct 18O/16O and 187Os/188Os compositions that can be explained through melting of pyroxenite-enriched peridotite mantle containing <10% recycled oceanic lithosphere. We also assess O-Os isotope systematics of lavas from Hawai‘i and the Azores and show that they also conform to addition of distinct recycled oceanic components, including lithosphere and pelagic sediment. We conclude that enriched isotopic signatures of some OIBs are consistent with pyroxenite-rich mantle sources metasomatized by recycled components.