Postcollisional exhumation history of the Tanzawa Tonalite Complex, inferred from (U-Th)/He thermochronology and fission track analysis
Postcollisional exhumation history of the Tanzawa Tonalite Complex, inferred from (U-Th)/He thermochronology and fission track analysis
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根据 (U-Th)/He 热年代学和裂变径迹分析推断的丹泽闪长岩杂岩碰撞后折返历史
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
T. Tagami
中科院分区：
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作者：
Kunimi Yamada;T. Tagami
[1]位于日本弧中部的南大沟地区的丹泽山脉是在过去几百万年间伊豆-小笠原弧与日本弧碰撞而形成的。丹泽英云闪长岩杂岩出露于丹泽山脉，推测代表伊豆-小笠原弧的中地壳。我们对该杂岩进行了新的热年代学测量，包括（U-Th）/He测年、裂变径迹测年和裂变径迹长度分析，以调查由弧-弧碰撞引起的Tanzawa Tonalite杂岩的折返历史。裂变径迹法测得磷灰石、锆石和锆石的（U-Th）/He年龄分别为2.0 ± 0.2Ma、3.3 ± 0.2Ma和4.5 ~ 6.9Ma。平均裂变径迹长度为9.7 ± 0.6 μm（2SE）。假设表面温度为10°C，计算出英云闪长岩的冷却速率为20°-60 ° C Ma−1（从2.7 Ma到3.3 Ma）、20 °-80 °C Ma−1（从3.3 Ma到2.0 Ma）和20 °-30 °C Ma−1（从2.0 Ma到0 Ma）。假设地热梯度为40°C km−1，计算出的折返速率为0.5至1.5 mm a−1（从3.7 Ma至3.3 Ma）、0.2 mm a−1（从3.3 Ma至2.0 Ma）和0.8 mm a−1（从2.0 Ma至0 Ma）。折返率并没有发生显着变化，尽管同时在Tanzawa山脉周围的构造变化后，0.7Ma。
[1] The Tanzawa Mountains in the South Fossa Magna region, in the middle of the Japan Arc, were formed due to collision of the Izu-Bonin Arc against the Japan Arc during the last several million years. The Tanzawa Tonalite Complex is exposed in the Tanzawa Mountains and is inferred to represent middle crust of the Izu-Bonin Arc. We performed new thermochronometry, consisting of (U-Th)/He dating, fission track dating, and fission track length analysis for the complex to investigate the exhumation history of the Tanzawa Tonalite Complex caused by arc-arc collision. Typical (U-Th)/He ages were 2.0 ± 0.2 Ma on apatite, 3.3 ± 0.2 Ma on zircon, and 4.5 to 6.9 Ma on zircon using the fission track method. The mean fission track length was 9.7 ± 0.6 μm (2 SE). The cooling rate of the tonalite has been calculated to be in the range of 20°–60°C Ma−1 from ∼7 to 3.3 Ma, ∼80°C Ma−1 from 3.3 to 2.0 Ma, and ∼30°C Ma−1 from 2.0 to 0 Ma assuming a surface temperature of 10°C. The exhumation rate has been calculated to be 0.5 to 1.5 mm a−1 from ∼7 to 3.3 Ma, ∼2 mm a−1 from 3.3 to 2.0 Ma, and ∼0.8 mm a−1 from 2.0 to 0 Ma with an assumed geothermal gradient of 40°C km−1. The exhumation rate has not changed significantly despite the simultaneous tectonic changes around the Tanzawa Mountains after ∼7 Ma.