Whole-rock chemical compositions including rare earth elements for the granitic rocks from the Hisakajima Island, Goto Archipelago, southwestern Japan were measured in order to constrain their origin and petrogenesis. The granites were divided into two types—a granodioritic group (GD) and a high Fe/Mg ratio granitic group (HFG). The granitic magma was formed by the upwelling of high-temperature mantle material, which might be related to the extension of the Japan Sea around the Middle Miocene. The origin of the GD magma was attributed to the mantle material, while the origin of the HFG magma was attributed to partial melting of the crust by upwelling of the high-temperature mantle. The amount of rare earth elements revealed the secondary addition of light rare earth elements through hydrothermal processes for the granites. Chondrite normalized rare earth element patterns revealed that the HFG rocks were not well differentiated.

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日本西南部五岛群岛久岛岛花岗岩岩的成因：地球化学研究

为了限制其起源和成岩作用，对来自日本西南部五岛群岛Hisakajima岛的花岗岩岩石中包括稀土元素的全岩石化学成分进行了测量，以限制其起源和成岩作用。花岗岩分为两种类型：花岗闪长岩群（GD）和高铁/镁比的花岗岩群（HFG）。花岗岩岩浆是由高温地幔物质的上升形成的，这可能与日本海在中新世中期周围的扩张有关。GD岩浆的起源归因于地幔物质，而HFG岩浆的起源归因于地幔因高温地幔上升而部分融化。稀土元素的量表明花岗岩是通过水热过程二次添加的轻稀土元素。