The spatial variation of initial 87Sr/86Sr ratios in the Toki granite, Central Japan: Implications for the intrusion and cooling processes of a granitic pluton
The spatial variation of initial 87Sr/86Sr ratios in the Toki granite, Central Japan: Implications for the intrusion and cooling processes of a granitic pluton
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日本中部土岐花岗岩中初始 87Sr/86Sr 比率的空间变化：对花岗岩岩体的侵入和冷却过程的影响
DOI：
10.2465/jmps.120801b
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发表时间：
2013
影响因子：
0.7
通讯作者：
T. Nishiyama
中科院分区：
文献类型：
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作者：
T. Yuguchi;T. Tsuruta;K. Hama;T. Nishiyama
日本中部土岐花岗岩中初始 Sr/Sr 比值 (SrI) 的空间变化显示出 0.708942 至 0.710069 范围内的异质性，这提供了有关岩体侵入和冷却过程的信息。土岐花岗岩具有三种矿物学岩相：白云母-黑云母花岗岩（MBG）、角闪石-黑云母花岗岩（HBG）和黑云母花岗岩（BG）。较大的SrI值分布在西缘（西MBG）和岩性中心区域（中部BG），而较小的SrI值分布在东北缘（东北MBG）。在土岐花岗岩中也发现了高和低 Sr 浓度的区域。在富含 Sr 的样品中，SrI (0.708942-0.709789) 随着 100/Sr (0.7-1.5) 的增加而增加。这种地球化学趋势延伸至米诺地体的乡村沉积岩，这可以解释为原始花岗质岩浆与米诺沉积岩之间同化和分步结晶（AFC）的结果。富 Sr 区域的 SrI 值显示出与氧化铝饱和指数 (ASI) 的相关性。特别是，西MBG具有较大的SrI值，被归类为具有较大ASI的过铝质花岗岩，表明岩体西缘在侵入过程中受到同化作用的强烈影响。 Srpoor 样品既存在于 SrI 值较大的中部 BG 中，也存在于 SrI 值较小的东北 MBG 中。贫Sr样品的ASI较小，分异指数较大，表明中部BG和东北MBG要么是由不同污染物含量的不同AFC过程产生的，要么是由不同SrI值的不同源岩浆的侵入和分异作用产生的。总体而言，托岐花岗岩中发现的地球化学空间变化可以通过岩浆房中不同程度的同化和分异结晶和/或多阶段侵入体（具有不同 SrI 值的多个源岩浆的不同结晶程度）来解释。此前的岩石学和热年代学研究表明，土岐花岗岩在低于500℃的冷却阶段从西缘壁面有效冷却。本研究中发现较大的SrI和ASI值对应于发生较早且较快冷却的西部边缘，这表明土岐花岗岩优先从围岩同化最广泛的过铝质边缘区域冷却。
The spatial variation in initial Sr/ Sr ratios (SrI) in the Toki granite, Central Japan, shows heterogeneity ranging from 0.708942 to 0.710069, which provides information on the intrusion and cooling processes of plutons. The Toki granite has three mineralogy-based rock facies: muscovite-biotite granite (MBG), hornblende-biotite granite (HBG) and biotite granite (BG). Large SrI values were found to be distributed at the western margin (west MBG) and the lithologically central region (central BG), while small SrI values were found at the northeast margin (northeast MBG). Regions with high and low Sr concentrations were also found in the Toki granite. In the Sr-rich samples, SrI (0.708942-0.709789) increases with 100/Sr (0.7-1.5). This geochemical trend extends towards the country sedimentary rocks of the Mino Terrane, which can be interpreted to result from assimilation and fractional crystallization (AFC) between the original granitic magma and the Mino sedimentary rocks. The SrI values in the Sr-rich regions show a correlation with the Alumina Saturation Index (ASI). In particular, the west MBG, with large SrI values, is classified as a peraluminous granitoid with large ASI, suggesting that the western margin of the pluton was strongly affected by assimilation during the intrusion process. The Srpoor samples are present both in the central BG, with large SrI values, and in the northeast MBG, with small SrI values. The Sr-poor samples have small ASI and large differentiation indices, indicating that the central BG and the northeast MBG were generated either by different AFC process with different amounts of contaminants or by the intrusion and fractionation of different source magma with different SrI values. Overall, the geochemical spatial variations found in the Toki granite can be explained by various degrees of assimilation and fractional crystallization in the magma chamber and/or multi-stage intrusions with different degrees of crystallization of plural source magmas with different SrI values. Previous petrographical and thermochronological studies revealed that the Toki granite effectively cooled from the wall at the western margin in the cooling stage at temperatures below 500 °C. Larger SrI and ASI values found in this study corresponded to the western margins where the earlier and more rapid cooling took place, indicating that the Toki granite was preferentially cooled from the peraluminous marginal regions where the assimilation of country rock was the most extensive.
日本西南部 Ryoke 带上原闪长岩中初始 87Sr/86Sr 比率异质性：来自磷灰石锶同位素分析的证据。
DOI：
--
发表时间：
2009
期刊：
Journal of Mineralogical and Petrological Sciences 104
影响因子：
--
作者：
Tsuboi;M.;Asahara;Y.
通讯作者：
Y.