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Research on interaction between slab melt and mantle peridotite : constraints from natural rocks and high pressure experiments

板片熔体与地幔橄榄岩相互作用研究:来自天然岩石和高压实验的约束

基本信息

批准号：
17540460
负责人：
SHINJOE Hironao
金额：
$ 1.54万
依托单位：
Tokyo Keizai University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

项目摘要

We have investigated igneous rocks from the regions where hot oceanic plate subducted, and carried out high pressure experiments, for the purpose of clarifying interaction between slab melt and mantle peridotite. The main results of our research is as follows.(1) We carried out high pressure experiments on the interaction between dacitic melt and olivine at 1 GPa corresponding with the depth of Moho. Trace element composition of run products were analyzed on laser ablation ICP-MS (LA-ICP-MS). Obtained opx and cpx crystals larger than 50 micrometers was analyzed and partition coefficients between pyroxenes and felsic melt on about 25 elements were determined. Partition coefficients of opx for incompatible elements including light REE to felsic melt are usually thought to be greater than those to mafic melt so far. However, we obtained values close to those reported for between opx and mafic melt.(2) Miocene near trench magmatism in the SW Japan arc was investigated. The magmatism was coeval with subduction of young hence hot Shikoku Basin of the Philippine Sea plate. Regional distribution of felsic igneous rocks formed by melting under high pressure with garnet residue was clarified. We also discussed the origin of voluminous S-type granitic melt formed in the region closed to the trench.(3) Along arc variation of whole rock compositions of the samples from Quaternary front volcanoes of the Southern Volcanic Zones in Andean arc was investigated. We found that contributions of the fluid derived from subducted sediment to the magma source increase as the age of the subducted plate beneath the volcano gets older.(4) Microanalysis of rock-forming minerals including zircon on the LA-ICP-MS was carried out, and obtained new data on the trace element partition coefficients and radiometric dating.

为了阐明板片熔体与地幔橄榄岩之间的相互作用，我们对大洋板块俯冲带的火成岩进行了研究，并进行了高压实验。我们的主要研究结果如下。(1)我们在1GPa对应于莫霍面深度的高压下进行了英安质熔体与橄榄石相互作用的实验研究。在激光烧蚀ICP-MS（LA-ICP-MS）上分析运行产物的微量元素组成。对获得的大于50微米的opx和cpx晶体进行了分析，并测定了约25种元素在辉石和长英质熔体之间的分配系数。轻稀土等不相容元素在长英质熔体中的分配系数通常大于在镁铁质熔体中的分配系数。然而，我们得到的值接近那些报道的氧化皮和镁铁质熔体之间。(2)对日本西南弧中新世海沟附近的岩浆活动进行了研究。岩浆活动与菲律宾海板块年轻而热的四国盆地的俯冲作用是同时代的。阐明了长英质岩浆岩的区域分布规律。本文还讨论了海沟附近大量S型花岗岩熔体的成因。(3)研究了安第斯弧南部火山带第四纪前缘火山岩样品全岩成分的沿着弧变化。我们发现，来自俯冲沉积物的流体对岩浆源的贡献随着火山下俯冲板块年龄的增大而增大。(4)利用LA-ICP-MS对该矿床的造岩矿物锆石进行了微量元素分析，获得了微量元素分配系数和放射性测年的新数据。