Cooling and inferred exhumation history of the Ryoke metamorphic belt in the Yanai district, south‐west Japan: Constraints from Rb–Sr and fission‐track ages of gneissose granitoid and numerical modeling
Cooling and inferred exhumation history of the Ryoke metamorphic belt in the Yanai district, south‐west Japan: Constraints from Rb–Sr and fission‐track ages of gneissose granitoid and numerical modeling
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日本西南部柳井地区 Ryoke 变质带的冷却和推断折返历史：来自片麻岩花岗岩裂变径迹年龄和 Rb-Sr 的约束以及数值模拟
DOI：
10.1111/j.1440-1738.2001.00312.x
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发表时间：
2001
期刊：
影响因子：
1.5
通讯作者：
Y. Ohtomo
中科院分区：
文献类型：
--
作者：
T. Okudaira;Y. Hayasaka;Osamu Himeno;Koichiro Watanabe;Y. Sakurai;Y. Ohtomo
摘要日本西南部的Ryoke变质带主要由I型花岗岩类及与之伴生的低压/高温变质岩组成。在柳爱区，它被划分为三个结构单元：北部、中部和南部。本文测定了中央构造单元片麻状花岗闪长岩的Rb-Sr全岩-矿物等时线年龄和裂变径迹年龄。四个Rb-Sr年龄落在约-87 Ma范围内。锆石和磷灰石的裂变径迹年龄分别为68.9±2.6 Ma和57.4±2.5 Ma(1σ误差)。结合新获得的年龄和已报道的(Th-)U-Pb年龄，热年代学研究揭示了两个明显的冷却阶段：1)峰期变质(~95 Ma)后不久的快速冷却阶段(~7Myr)；2)约88 Ma后的缓慢冷却阶段(~5℃/Myr)。第一个快速冷却阶段对应于侵入的花岗闪长岩浆及其伴生变质岩的热弛豫，以及岩浆侵入后不久开始的沿低角度断裂的位移隆升。后期变形的抬升作用形成了大规模的直立褶皱，导致了第一阶段折返的进行。该阶段的平均折返速度为≥2 mm/a。第二阶段岩石不伴生韧性变形，折返速率为0.1~0.2 mm/a。第一和第二冷却阶段折返速度的差异是造山作用早期和晚期地壳厚度和韧性变形活动不同的结果。
Abstract The Ryoke metamorphic belt in south‐west Japan consists mainly of I‐type granitoids and associated low‐pressure/high‐temperature metamorphic rocks. In the Yanai district, it has been divided into three structural units: northern, central and southern units. In this study, we measured the Rb–Sr whole‐rock–mineral isochron ages and fission‐track ages of the gneissose granodiorite in the central structural unit. Four Rb–Sr ages fall in a range of ca 89–87 Ma. The fission‐track ages of zircon and apatite are 68.9 ± 2.6 Ma and 57.4 ± 2.5 Ma (1σ error), respectively. Combining the newly obtained ages with previously reported (Th–)U–Pb ages from the same unit, thermochronologic study revealed two distinctive cooling stages; 1) a rapid cooling (> 40°C/Myr) for a period (~7 Myr) soon after the peak metamorphism (~ 95 Ma) and 2) the subsequent slow cooling stage (~ 5°C/Myr) after ca 88 Ma. The first rapid cooling stage corresponds to thermal relaxation of the intruded granodiorite magma and its associated metamorphic rocks, and to the uplift by a displacement along low‐angle faults which initiated soon after the intrusion of the magma. Uplift by the later stage deformation having formed large‐scale upright folds resulted in progress of the exhumation during the first stage. The average exhumation velocity of the stage is ≥ 2 mm/yr. During the second stage, the rocks were not accompanied by ductile deformation and were exhumed with the rate of 0.1–0.2 mm/yr. The difference in the exhumation velocity between the first and second cooling stages resulted from the difference in the thickness of the crust and in the activity of ductile deformation between the early and later stages of the orogenesis.
影响因子：
3.4
作者：
Michael Brown
通讯作者：
Michael Brown
日本西南部 Ryoke 变质带的热演化：构造和数值模拟：评论
DOI：
--
发表时间：
2002
期刊：
The Island Arc 11
影响因子：
--
作者：
Yasutaka Y;Wallis S;Ikeda T
通讯作者：
Ikeda T
共轭稳定自由基光激发高自旋有机分子的设计、合成和物理性质，旨在通过光激发态表达复杂功能（IV）
DOI：
--
发表时间：
2005
期刊：
影响因子：
--
作者：
東一 哲也;手木 芳男
通讯作者：
手木 芳男