The early Miocene (~25 Ma) volcanism in the northern Kyushu-Palau Ridge, enriched mantle source injection during rifting prior to the Shikoku backarc basin opening
The early Miocene (~25 Ma) volcanism in the northern Kyushu-Palau Ridge, enriched mantle source injection during rifting prior to the Shikoku backarc basin opening
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DOI：
10.1007/s00410-011-0680-x
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发表时间：
2012-03
影响因子：
3.5
通讯作者：
S. Haraguchi;T. Ishii;J. Kimura;Y. Kato
中科院分区：
文献类型：
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作者：
S. Haraguchi;T. Ishii;J. Kimura;Y. Kato
北方九州-帕劳海脊（KPR）是伊豆-小笠原（小笠原）-马里亚纳（IBM）活动弧的残余共轭弧，除小马桥-大仁海山外，其余均为玄武岩-安山岩。这些基性到中质火山岩是由与四国盆地扩张相关的原始IBM弧中的裂谷火山作用产生的。这些火山岩的HFSE和HREE含量和比值表明，丰富的源地幔成分相比，现代火山前缘。LILE比值表现出类似的特点，最近伊豆弧后火山作用，和一些富集的火山岩表现出高丰度的沉积物熔融输入。根据这些观测结果和对已发表数据集的汇编，IBM弧下楔状地幔的置换事件发生了两次。第一次事件发生在45 ~ 38 Ma之间，太平洋型地幔被亏损的印度型地幔所取代。第二次事件发生在36 ~ 25 Ma，富集地幔从弧后一侧流出。在原始IBM弧裂谷板组件是一个类似的特点，最近弧后火山活动的伊豆弧，沉积物熔融增加在局部地区。
The northern Kyushu-Palau Ridge (KPR), remnant conjugate arc of the Izu-Ogasawara (Bonin)-Mariana (IBM) active arc, is dominated by basalt-andesite except for the Komahashi-Daini Seamount where acidic plutonic rocks of 38 Ma were recovered. These mafic to intermediate volcanics are produced by the rifting volcanism in the proto-IBM arc associated with spreading of the Shikoku Basin. The HFSE and HREE contents and ratios of these volcanics indicate enriched source mantle composition compared to recent volcanic front. The LILE ratios exhibit similar characteristics to reararc volcanism of the recent Izu arc, and some enriched volcanics exhibit high abundance of sediment melt inputs. Based on these observations and compilations of the published data set, the replacement event of the wedge mantle under the IBM arc occurred two times. The first event occurred between 45 and 38 Ma, with Pacific type mantle being replaced by depleted Indian type mantle. The second event occurred between 36 and 25 Ma, enriched mantle flowed from reararc side. The slab component during the proto-IBM arc rifting was a similar characteristic to recent reararc volcanism of the Izu arc, and sediment melt added in a local area.