Exhumation rates and age of metamorphism in the Sanbagawa belt: new constraints from zircon fission track analysis
Exhumation rates and age of metamorphism in the Sanbagawa belt: new constraints from zircon fission track analysis
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三波川带折返率和变质年龄：锆石裂变径迹分析的新约束
DOI：
10.1111/j.1525-1314.2003.00493.x
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发表时间：
2004
影响因子：
3.4
通讯作者：
T. Tagami
中科院分区：
文献类型：
--
作者：
S. Wallis;Y. Moriyama;T. Tagami
桑巴加瓦带ASemigawa区高品位部分的锆石裂变径迹年龄和径迹长度分析表明，63.2 ± 5.8(2 σ)Ma经历了一段简单的冷却历史。结合多硅白云母、角闪石K-Ar和40Ar/39Ar测年结果，得出冷却速率为6-13 °C-MYR−1，利用已知的P-T路径形状可换算为最大折返速率为0.70 mm−1。这比掘尸历史的早期要低一个数量级。相比之下，低品位鄂博克地区的锆石裂变径迹分析表明，该地区经历了一段复杂的热史，可能与早于约30 Ma的造山后二次再加热有关。这一事件可能与15 Ma左右日本西南部广泛的火成岩活动有关。鄂博克地区与俯冲有关的变质作用年龄可能比人们普遍接受的77-70 Ma范围要早得多。
Zircon fission track dating and track length analysis in the high‐grade part of the Asemigawa region of the Sanbagawa belt demonstrates a simple cooling history passing through the partial annealing zone at 63.2 ± 5.8 (2 σ) Ma. Combining this age with previous results of phengite and amphibole K–Ar and 40Ar/39Ar dating gives a cooling rate of between 6 and 13 °C Myr−1, which can be converted to a maximum exhumation rate of 0.7 mm year−1 using the known shape of the P–T path. This is an order of magnitude lower than the early part of the exhumation history. In contrast, zircon fission track analyses in the low‐grade Oboke region show that this area has undergone a complex thermal history probably related to post‐orogenic secondary reheating younger than c. 30 Ma. This event may correlate with the widespread igneous activity in south‐west Japan around 15 Ma. The age of subduction‐related metamorphism in the Oboke area is probably considerably older than the generally accepted range of 77–70 Ma.