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Formation and modification of the mantle wedge : from the ocean to the confinent

地幔楔的形成和改造：从海洋到大陆

基本信息

批准号：
13440161
负责人：
ARAI Shoji
金额：
$ 5.18万
依托单位：
KANAZAWA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

Orthopyroxene-rich xenoliths from Tallante, Spain, and Takashima, SW Japan, have been investigated. They were farmed by a reaction between the slab melt(adakite melt) and the mantle peridotite. Their dinopyroxene is similar in trace-element characteristics and REE pattern to clinopyroxene phenocrystin adakite from Adak Island of the Aeutian arc. This may indicate that an adakitic melt was involved information of the opx-rich pyroxenite xenoliths from Tallante and Takashima. They possibly derived from the conduit of adakitic melt within the mantle wedge. The chemical compositional trend of adakite is, therefore, basically controlled by precipitation of orthopyroxene at the expense of olivine. The orthopyroxenite from Tallante contains some HFSE-rich minerals such as Nb-rich rutile, and is enriched with HFSE relative to LILE. This means that the reaction above can yield negative spikes of HFSE to the fractionating slab-derived melt. The orthopyroxene in such pyroxenites, interpereted here to be a slab-melt/peridotite reaction product, is distinctively different from the oryhopyroxene that is interpreted to be fluid/peridotite reaction product, described from Avahc and Iraya volcanoes. We have stated a geochemical analysis of metamorphosed/metasomatized peridotite of the Ochiai-Hokubo comprex, emplaced into the Sangun highP/low T schist, as an analogue to mantle-wedge peridotite interacting with slab. The peridotite is clearly enriched with Rb and Cs in addition to H2O, and these dements are concentrated in metasomatically formed Na-trermolite.

对西班牙Tallante和日本西南部Takashima的富正辉石捕虏体进行了研究。它们是由板块熔体（埃达克岩熔体）和地幔橄榄岩之间的反应形成的。它们的二辉石在微量元素特征和稀土模式上与阿乌提弧阿达克岛的斜辉石苯晶埃达克岩相似。这可能表明，塔兰特和高岛富透明辉石岩捕虏体的信息与埃达克质熔体有关。它们可能来源于地幔楔内的埃达克质熔体管道。因此，埃达克岩的化学成分趋势基本上是由正辉石的沉淀而牺牲橄榄石来控制的。塔兰特正辉石中含有富铌金红石等富氢硒矿物，相对于LILE富氢硒。这意味着上述反应可以对分馏板衍生熔体产生负峰值的HFSE。这种辉石岩中的正辉石被解释为板熔体/橄榄岩反应产物，与Avahc和Iraya火山中描述的被解释为流体/橄榄岩反应产物的橄榄辉石明显不同。本文对位于三关高p /低T片岩中的Ochiai-Hokubo杂岩的变质/交代橄榄岩进行了地球化学分析，认为其类似于幔楔橄榄岩与板岩的相互作用。橄榄岩除H2O外，Rb和Cs富集，这些元素富集在交代形成的na -闪莫石中。