Cooling processes of a dolerite sill inferred from the variations in plagioclase aspect ratio, Atsumi District, north-eastern Japan
Cooling processes of a dolerite sill inferred from the variations in plagioclase aspect ratio, Atsumi District, north-eastern Japan
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日本东北部渥美地区斜长石纵横比变化推断的辉绿岩基台的冷却过程
DOI：
10.1007/s12303-021-0038-y
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发表时间：
2021
影响因子：
1.2
通讯作者：
Hoshide Takashi
中科院分区：
文献类型：
--
作者：
Kondo Kentaro;Hoshide Takashi
日本东北部厚见地区的上茅冈岩片具有碱性玄武岩成分。模式橄榄石和镍的富集在较低的部分的席表明早期形成的橄榄石晶体的积累。总的来说，斜长石的平均长宽比从岩片的中心部分向顶部和底部边缘增加。斜长石的平均纵横比和计算的结晶时间在每个高度的片，除了最低的边缘，大致绘制回归线附近的基础上绘制的许多窗台在以前的研究。然而，我们观察到，斜长石的平均纵横比在一些层位的中央部分的片材表现出从回归线的偏移。在片的中央部分的橄榄石方沸石粗玄岩富含沸石杏仁和玻璃质中稳态淬火结构。这些观察结果表明，在板的中心部分的冷却速率是更快的相比，假设仅传导冷却。在板中心快速冷却的一个合理机制是渗透到柱状接头的海水对流的热传递。
The upper Kayaoka sheet in the Atsumi area, Northeast Japan, has an alkaline-basaltic composition. The modal olivine and Ni enrichment in the lower part of the sheet indicates the accumulation of early formed olivine crystals. Overall, the average aspect ratio of plagioclase increases from the central part of the sheet toward both the top and bottom margins. The average aspect ratios of plagioclase and calculated crystallisation times at each height of the sheet, except for the lowermost margin, are roughly plotted near the regression line drawn based on those from many sills in previous research. However, we observed that the average aspect ratios of plagioclase in some horizons of the central part of the sheet exhibit an offset from the regression line. The olivine analcite dolerite in the central part of the sheet is rich in zeolite amygdules and glassy mesostasis with a quench texture. These observations suggest that the cooling rate in the central part of the sheet was faster compared with assuming conductive cooling only. A plausible mechanism for the rapid cooling at the centre of the sheet is heat transport by the convection of seawater that has infiltrated the columnar joint.