Abstract

The Seven Devils Mountains are located in the Wallowa-Whitman National Forest in western Idaho. These mountains expose a geologically complex and variably metamorphosed terrane which preserves the Permo-Triassic volcanic arc accreted against the Cordilleran margin. Due to its geologic complexity, the origins of the Seven Devils Mountains and therin correlations between it, the Wrangellia terrane, and Blue Mountains Province terranes are uncertain. Zircon U/Pb and Lu/Hf analyses were used to enhance the geologic history of this complex terrane and act as steppingstone for further work in testing proposed ties to the Wrangellia and Blue Mountains Province terranes. LA-ICP-MS zircon U/Pb dating on six samples of intermediate intrusive rocks yield ages ranging from 120.1 to 137 Ma with the average age of 127 Ma. All samples have similar Lu/Hf isotopic compositions, with a range in εHf(t) of 8.6 to 13.8 with the average εHf(t) value of 10.8. Isotopic and age data show that intrusive rocks were forming close to the time of accretion. These new data combined with previous age and isotope data shows more similarities between the Seven Devils volcanic arc and the Blue Mountains Province than the Wrangellia terrane, however more extensive research is needed to truly decipher the complex history of these amalgamated terranes.

中文翻译：

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基于锆石 U/Pb 年代学和侵入体的 Hf 同位素地球化学的七魔鬼火山弧演化和与北美克拉通的并合期，西爱达荷州（美国）

摘要

七魔鬼山位于爱达荷州西部的瓦洛瓦-惠特曼国家森林中。这些山脉暴露出地质复杂且变质多变的地体，保留了在科迪勒拉山脉边缘增生的二叠纪-三叠纪火山弧。由于其地质复杂性，七怪山的起源及其与兰格利亚地体和蓝山省地体之间的相关性尚不确定。锆石 U/Pb 和 Lu/Hf 分析被用来增强这个复杂地体的地质历史，并作为进一步测试与 Wrangellia 和蓝山省地体的联系的进一步工作的垫脚石。LA-ICP-MS 锆石 U/Pb 定年对 6 个中侵入岩样品产生年龄范围从 120.1 到 137 Ma，平均年龄为 127 Ma。t ) 为 8.6 到 13.8，平均 εHf( t ) 值为 10.8。同位素和年龄数据显示侵入岩在接近增生时间时形成。这些新数据与之前的年龄和同位素数据相结合，表明七魔火山弧和蓝山省之间的相似性比兰格利亚地体更多，但需要更广泛的研究才能真正破译这些混合地体的复杂历史。