Transportation process of transitional-metal elements by fluid and/or melt in the upper mantle beneath the arc

我们研究了两种不同类型的地幔衍生橄榄岩，以阐明变质过程，特别是通过熔体或板源流体对过渡金属元素的运输：一种是来自火山锋下弧次地幔的捕虏体，另一种是阿曼蛇绿岩底部的固体侵入橄榄岩块体和橄榄岩。结果表明，火山锋下的次弧地幔高度交代，部分元素(如：例如，Ni， Fe和铂族元素)部分集中在那里。此外，在弧下地幔捕虏体中发现了含h_2o包裹体。然而，即使在弧源物质中也有相当多的H_2O包裹体的报道，我们确认H_2O是火山锋下亚弧上地幔内的主要流体相。

We examined two different types of mantle-derived peridotites to clarify modification processes, especially to transportation of transitional-metal elements, by melts or slab-derived fluids : the one is xenoliths from sub-arc mantle beneath the volcanic front and the other is solid intrusive peridotite blocks and peridotites at the bottom of Oman ophiolite. Then, we identified that the sub-arc mantle beneath the volcanic front is highly metasomatized and some elements(e. g., Ni, Fe and platinum-group elements) are partly concentrated in there. In addition, we found H_2O-bearing inclusions in sub-arc mantle xenoliths. However there have been quite a few reports of H_2O inclusions even in arc-derived materials, we confirmed that H_2O is the main fluid phase within the sub-arc upper mantle beneath the volcanic front.