Water content, δD and δ11B tracking in the Vanuatu arc magmas (Aoba Island): Insights from olivine-hosted melt inclusions
Water content, δD and δ11B tracking in the Vanuatu arc magmas (Aoba Island): Insights from olivine-hosted melt inclusions
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瓦努阿图岛弧岩浆（奥巴岛）的含水量、δD 和 δ11B 追踪：来自橄榄石熔融包裹体的见解
DOI：
10.1016/j.lithos.2014.08.011
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发表时间：
2014
期刊：
影响因子：
3.5
通讯作者：
E. Deloule
中科院分区：
文献类型：
--
作者：
N. Métrich;E. Deloule
本文报道了瓦努阿图岛中部(西南太平洋)奥巴岛碱性玄武岩系列熔体包裹体的H、B同位素比值和H2O、B及微量元素含量的离子探针测量结果。熔体包裹体赋存于橄榄石FO86-90中，具有很大的微量元素浓度和氢(δD来自−48.2至+61.7‰)和硼(δ11B来自−11.9至+66.4‰)同位素组成。在一小部分熔融包裹体中观察到的高氘富集(δD和≥0‰)需要通过橄榄石网络的质子扩散损失，以及晚期岩浆与含水盐水流体的相互作用。因此，这些熔融包裹体不被认为是橄榄石生长的岩浆的代表。在大多数熔体包裹体中，H2O、K2O、Ba和Sr的正相关使我们确定了敖巴岛玄武岩的K2O/H2O(1.5M±0.02)、H2O/Ba值(46.00±0.03×10−/4)和H2O/Sr值(29.0±0.02×0.10−/4)。δ11B、B/Nb和B/ND的总体对比证实了板片流体之间的混合，优先富含δ11B和流体活动元素，以及相对亏损的MORB型地幔楔体。Heavyδ11B(平均5.4T±10.7‰)指示板岩来源的流体，可能涉及蛇纹石，其平均δD值为−(28.4T±17.7‰)。奥巴岩浆(熔体包裹体)记录的化学和同位素变异性与瓦努阿图弧中段山脊-弧碰撞的地球动力学背景相一致。
Ion microprobe measurements of H and B isotopic ratios and H2O, B and trace element contents are reported here for a series of melt inclusions typical of alkaline basalts of Aoba Island in the central part of Vanuatu arc (Southwestern Pacific). The melt inclusions, hosted in olivine Fo86–90, display large ranges in trace element concentrations and hydrogen (δD from − 48.2 to + 61.7‰) and boron (δ11B from − 11.9 to + 6.4‰) isotopic compositions. The high deuterium enrichment (δD ≥ 0‰) observed in a small subset of melt inclusions requires a proton diffusion loss through the olivine network, in addition to late-stage magma interactions with aqueous saline fluids. These melt inclusions are therefore not considered as representative of the magma from which the olivine grew. In most melt inclusions, positive correlations between H2O, K2O, Ba and Sr lead us to determine the K2O/H2O (1.5 ± 0.2), H2O/Ba (46 ± 3 × 10− 4) and H2O/Sr (29 ± 2 × 10− 4) ratios of Aoba basalts.Overall correlations between δ11B, B/Nb, and B/Nd testify to the mixing between slab-derived fluids, preferentially enriched in δ11B and fluid mobile elements and a relatively depleted MORB-type mantle wedge beneath Aoba Island. Heavy δ11B (on average 5.4 ± 0.7‰) indicate slab-derived fluids, possibly involving serpentine, which would have a mean δD value of − 28.4 ± 7‰. The chemical and isotopic variability recorded by Aoba magmas (melt inclusions) is consistent with the geodynamic context of ridge-arc collision in the central segment of Vanuatu arc.
影响因子：
3.5
作者：
Jochum, Klaus Peter;Stoll, Brigitte;Woodhead, Jon D.
通讯作者：
Woodhead, Jon D.