Garnet-field melting and late-stage refertilization in 'residual' abyssal peridotites from the Central Indian Ridge
Garnet-field melting and late-stage refertilization in 'residual' abyssal peridotites from the Central Indian Ridge
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DOI：
10.1093/petrology/43.12.2305
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发表时间：
2002-12-01
影响因子：
3.9
通讯作者：
Hofmann, AW
中科院分区：
文献类型：
--
作者：
Hellebrand, E;Snow, JE;Hofmann, AW
残留的石榴石在大洋中脊之下融化过程中的作用一直是最近许多研究的主题。为了从熔融残留物的角度解决这一问题，我们获得了中印度海岭残留的深海橄榄岩的主量元素和微量元素矿物化学。许多单斜辉石的中重稀土元素比值(MREE/HREE)太低，不能仅用尖晶石橄榄岩稳定区的熔融来解释。在石榴石橄榄岩稳定区，一定有百分之几的熔融发生在较高的压力下。应用新的微量元素分配模型预测HREE在高压单斜辉石中是相容的，但不能完全解释MREE从HREE中的分馏。此外，许多样品显示了参考的质地和化学证据，例如高度不相容的微量元素相对于中等不相容的微量元素的相对富集度。因此，从主要和中等不相容的微量元素中分离出来的高度不相容的元素，对于评估熔体圈闭、熔岩反应和脉化等后期过程是有用的。中等不相容的微量元素受这种晚期作用的影响较小，因此有助于推断深海橄榄岩的熔融历史。
The role of residual garnet during melting beneath mid-ocean ridges has been the subject of many recent investigations. To address this issue from the perspective of melting residues, we obtained major and trace element mineral chemistry of residual abyssal peridotites from the Central Indian Ridge. Many clinopyroxenes have ratios of middle to heavy rare earth elements (MREE/HREE) that are too low to be explained by melting in the stability field of spinel peridotite alone. Several percent of melting must have occurred at higher pressures in the garnet peridotite stability field. Application of new trace element partitioning models, which predict that HREE are compatible in high-pressure clinopyroxene, cannot fully explain the fractionation of the MREE from the HREE. Further, many samples show textural and chemical evidence for refertilization, such as relative enrichments of highly incompatible trace elements with respect to moderately incompatible trace elements. Therefore, highly incompatible elements, which are decoupled from major and moderately incompatible trace elements, are useful to assess late-stage processes, such as melt entrapment, melt-rock reaction and veining. Moderately incompatible trace elements are less affected by such late-stage processes and thus useful to infer the melting history of abyssal peridotites.