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Geological and petrological study of the middle Miocene regional basalts from the Japan Sea side in the NE Japan arc

日本东北弧日本海一侧中新世区域玄武岩的地质和岩石学研究

基本信息

批准号：
62540617
负责人：
SHUTO Kenji
金额：
$ 1.09万
依托单位：
Niigata University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1989
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-62540617/
关键词：
The Northeast Japan Arc Lateral Variation of LIL Elements Non Island Arc-Type Volcanic Rock Late Miocene (8-6 Ma) Volcanic Rock Pliocene (4-2 Ma) Volcanic Rock Middle Miocene (16-14 Ma) Volcanic Rock Plate Subduction Mantle Diapir 後期中新世(8〜

项目摘要

Abundances of major elements and seven trace elements, Rb, Sr, Nb, Y, Zr, Ni and Cr were determined by X-ray fluorescence analysis for 111 samples from twelve Pliocene volcanic centers in the NE Japan are. The petrographical and analytical results in this study and the published ones on other Pliocene volcanic rocks indicate that systematic zonal variation of petrological features, i.e., mafic phenocryst assemblages and rock series, as well as gradual increase in K_2O, Rb and Sr contents are recognized in the Pliocene volcanic rocks from the Pacific Ocean side to the Japan Sea side across the NE Japan arc. Furthermore, systematic across-arc variation of chemical compositions and petrological features, similar to those in the Pliocene to Quaternary volcanic rocks, are also observed in the late Miocene (8-6 Ma) volcanic rocks throughout the NE Japan arc.Similarity of across-arc variation. with regard to both the petrological and geochemical features among the volcanic rocks from the late … More Miocene to Quaternary through Pliocene time suggests that igneous activity which is related to a mechanism for magma generation determined by plate subduction bas been continuous in the NE Japan arc at least during 8 Ma ago to the present.On the other hand, the NE Japan arc of the middle Miocene (16-14 Ma) are characterized by occurrence of rocks of non island arc-type volcanic rocks such as E-type MORB like basalt which is enriched in Ti and other HFS elements, basaltic rocks hailing intermediate nature between the island arc tholeiite and the back arc basin basalt in bulk rock chemistry and icelandite like andesite and dacite, in association with volcanics of the island arc tholeiite series and calc-alkaline series. These volcanic rocks increase gradually in K_2O from the Japan Sea side toward the Pacific Ocean side across the NE Japan arc, indicating the lateral variations dissimilar to the case of volcanic rocks produced during 8 Ma ago to the present.It is possible that such non island arc-type volcanics were derived from a upper mantle material which is different from the present one in the NE Japan arc. These volcanics could have been generated from a mantle diapir ascending from asthenosphere during the spreading of the Japan Sea. The middle Miocene volcanics of island arc tholeiite series and calc-alkaline series in the NE Japan arc may have been originated from partial melting of upper mantle and lower crust heated by the ascending mantle diapir. Less

本文用X射线荧光分析法测定了日本东北部12个上新世火山中心111个样品的主量元素和Rb、Sr、Nb、Y、Zr、Ni、Cr等7种微量元素的丰度。本研究的岩石学和分析结果以及已发表的其他上新世火山岩的岩石学和分析结果表明，岩石学特征的系统地带性变化，即，沿日本弧东北方向，从太平洋一侧向日本海一侧，上新世火山岩中的K_2O、Rb和Sr含量逐渐增加，并具有镁铁质斑晶组合和岩石系列。此外，在整个东北日本弧的晚中新世（8-6 Ma）火山岩中也观察到了与上新世-第四纪火山岩相似的化学成分和岩石学特征的系统性弧间变化。晚白垩世以来火山岩的岩石学和地球化学特征 ...更多信息中新世至第四纪至上新世的时间表明，至少在8 Ma前至今，与板块俯冲所决定的岩浆生成机制有关的岩浆活动在日本东北弧一直是持续的。中新世中期日本东北弧（16-14 Ma）以产自非岛弧型火山岩（如E型MORB类玄武岩）为特征，富Ti等HFS元素，玄武质岩石在整体岩石化学上海陵岛弧拉斑玄武岩和弧后盆地玄武岩之间，与岛弧拉斑玄武岩系列和钙碱性系列的火山岩有关，这些火山岩的K_2O含量从日本海一侧向太平洋一侧逐渐增加，表明其横向变化与8 Ma前至今的火山岩不同，这类非岛弧型火山岩可能来自与现今东北日本弧不同的上地幔物质。这些火山岩可能是在日本海扩张过程中从软流圈上升的地幔底辟作用的产物。日本弧东北部中中新世岛弧拉斑玄武岩系列和钙碱性系列火山岩可能是由地幔底辟上升加热的上地幔和下地壳部分熔融形成的。少