Insights into Petrological Characteristics of the Lithosphere of Mantle Wedge beneath Arcs through Peridotite Xenoliths: a Review
Insights into Petrological Characteristics of the Lithosphere of Mantle Wedge beneath Arcs through Peridotite Xenoliths: a Review
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DOI：
10.1093/petrology/egm069
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发表时间：
2007-10
影响因子：
3.9
通讯作者：
S. Arai;S. Ishimaru
中科院分区：
文献类型：
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作者：
S. Arai;S. Ishimaru
通过对西太平洋岛弧（堪察加、日本东北、日本西南、吕宋-台湾、新爱尔兰和瓦努阿图）岩石圈地幔中橄榄岩捕虏体岩石学特征的研究，对成熟俯冲系统中的超俯冲带地幔进行了综述。然后将这些数据与文献中描述的最近或更老的弧（例如新不列颠，加拿大西部到美国，墨西哥中部，巴塔哥尼亚，小安的列斯群岛和潘诺尼亚盆地）的橄榄岩捕虏体进行比较，以建立弧下岩石圈地幔的岩石学模型。在目前活跃的火山弧中，橄榄岩中记录的部分熔融程度似乎从弧前到弧后区域逐渐减少。高度亏损的方辉橄榄岩，比深海方辉橄榄岩更亏损，只出现在前缘弧到弧前区域。无论弧后盆地是否发育，亏损程度再次增加，达到与弧后伸展区内亏损最严重的深海方辉橄榄岩相似的程度。交代作用是最突出的火山前，岩浆生产率最高的地方，二氧化硅富集，涉及的次生斜方辉石的交代形成在橄榄石的费用，是很重要的，在这个地区，因为除了板派生的硅质流体。一些明显的原生正辉石，如那些在方辉橄榄岩从小安的列斯群岛弧，可能是这种次生共生，但已重结晶，使置换结构丢失。岛弧下岩石圈地幔橄榄岩中的含水矿物Ti含量相对较低。交代型含水矿物的K/Na比值从弧前地幔向后降低，在岩石圈地幔内部也是如此。岩石圈地幔楔橄榄岩，特别是来自火山前缘以下的交代橄榄岩，是高度氧化的。地幔楔的剪切作用预计在火山前缘下方，并以细粒橄榄岩捕虏体为代表。
The petrological characteristics of peridotite xenoliths exhumed from the lithospheric mantle below the Western Pacific arcs (Kamchatka, NE Japan, SW Japan, Luzon-Taiwan, New Ireland and Vanuatu) are reviewed to obtain an overview of the supra-subduction zone mantle in mature subduction systems. These data are then compared with those for peridotite xenoliths from recent or older arcs described in the literature (e.g. New Britain, Western Canada to USA, Central Mexico, Patagonia, Lesser Antilles and Pannonian Basin) to establish a petrological model of the lithospheric mantle beneath the arc. In currently active volcanic arcs, the degree of partial melting recorded in the peridotites appears to decrease away from the fore-arc towards the back-arc region. Highly depleted harzburgites, more depleted than abyssal harzburgites, occur only in the frontal arc to fore-arc region. The degree of depletion increases again to a degree similar to that of the most depleted abyssal harzburgites within the back-arc extensional region, whether or not a back-arc basin is developed. Metasomatism is most prominent beneath the volcanic front, where the magma production rate is highest; silica enrichment, involving the metasomatic formation of secondary orthopyroxene at the expense of olivine, is important in this region because of the addition of slab-derived siliceous fluids. Some apparently primary orthopyroxenes, such as those in harzburgites from the Lesser Antilles arc, could possibly be of this secondary paragenesis but have been recrystallized such that the replacement texture is lost. The Ti content of hydrous minerals is relatively low in the sub-arc lithospheric mantle peridotites. The K/Na ratio of the metasomatic hydrous minerals decreases rearward from the fore-arc mantle as well as downward within the lithospheric mantle. The lithospheric mantle wedge peridotites, especially metasomatized ones from below the volcanic front, are highly oxidized. Shearing of the mantle wedge is expected beneath the volcanic front, and is represented by fine-grained peridotite xenoliths.