Ito Hisatoshi, Spencer Christopher J, Danišík Martin, Hoiland Carl W
Geosphere Science Sector, Central Research Institute of Electric Power Industry, Chiba, 270-1194, Japan.
Earth Dynamics Research Group, Department of Applied Geology, The Institute of Geoscience Research (TIGeR), Curtin University, Perth, WA, 6845, Australia.
Sci Rep. 2017 Sep 29;7(1):12457. doi: 10.1038/s41598-017-12790-w.
Plutons are formed by protracted crystallization of magma bodies several kilometers deep within the crust. The temporal frequency (i.e. episodicity or 'tempo') of pluton formation is often poorly constrained as timescales of pluton formation are largely variable and may be difficult to resolve by traditional dating methods. The Hida Mountain Range of central Japan hosts the youngest exposed plutons on Earth and provides a unique opportunity to assess the temporal and spatial characteristics of pluton emplacement at high temporal resolution. Here we apply U-Pb geochronology to zircon from the Quaternary Kurobegawa Granite and Takidani Granodiorite in the Hida Mountain Range, and from modern river sediments whose fluvial catchments include these plutons in order to reconstruct their formation. The U-Pb data demonstrate that the Kurobegawa pluton experienced two magmatic pulses at ~2.3 Ma and ~0.9 Ma; whereas, to the south, the Takidani pluton experienced only one magmatic pulse at ~1.6 Ma. These data imply that each of these magmatic systems were both spatially and temporally distinct. The apparent ~0.7 Myr age gap between each of the three magmatic pulses potentially constrains the recharge duration of a single pluton within a larger arc plutonic complex.
深成岩体是由地壳内数千米深处的岩浆体长期结晶形成的。由于深成岩体形成的时间尺度变化很大，传统测年方法可能难以解析，因此深成岩体形成的时间频率（即间歇性或“节奏”）往往难以确定。日本中部的飞驒山脉拥有地球上最年轻的出露深成岩体，为以高时间分辨率评估深成岩体侵位的时空特征提供了独特的机会。在此，我们对飞驒山脉第四纪黑部川花岗岩和滝谷花岗闪长岩中的锆石以及现代河流沉积物（其流域包括这些深成岩体）应用铀铅年代学，以重建它们的形成过程。铀铅数据表明，黑部川深成岩体在约230万年和约90万年前经历了两次岩浆脉冲；而在南部，滝谷深成岩体仅在约160万年前经历了一次岩浆脉冲。这些数据表明，这些岩浆系统在空间和时间上都是不同的。这三次岩浆脉冲之间约70万年的明显年龄间隔可能限制了单个深成岩体在更大的弧形深成岩复合体中的补给持续时间。
