...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Geological Society of America Bulletin >Implications of middle Eocene epizonal plutonism for the unroofing history ofthe bitterroot metamorphic core complex, Idaho-Montana
【24h】

Implications of middle Eocene epizonal plutonism for the unroofing history ofthe bitterroot metamorphic core complex, Idaho-Montana

机译：中始新世上层带云岩现象对苦根变质核复合体爱达荷-蒙大拿州的顶顶历史的影响

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Petrologic and geochronologic limits on the progression of east-directed extensional unroofing of the Bitterroot metamorphic core complex provide a means to compare rates of denudation across the footwall during the early stages of extensional denudation. U-Pb and ~(40)Ar/~(39)Ar data from epizonal plutons in the northwestern and southwestern Bitterroot metamorphic core complex demonstrate that much of the western footwall was exhumed to shallow levels (1-5 km) by ca. 49 Ma, while eastern footwall rocks remained at high temperatures following an episode of isothermal decompression, U-Pb ages of epizonal plutons along the western margins of the footwall suggest that as much as 13 km of unroofing occurred between anatectic melting of Belt Supergroup metasedimentary rocks in the western footwall no later than 56 Ma and emplacement of the adjacent epizonal Lolo Hot Springs batholith at ca. 49 Ma in the northwestern Bitterroot Range. Tectonic denudation during this interval removed roughly the same amount of overburden from eastern footwall rocks, suggesting that the initial stages of unroofing may have been accommodated by a planar, moderately east-dipping (30deg-50deg) shear zone. ~(40)Ar/~(39)Ar cooling data show that cooling in the western footwall was synchronous with unroofing. In contrast, we suggest that a significant delay in cooling of eastern footwall rocks may have resulted fro ma slight increase in geothermal gradient following this unroofing stage. Exposure of a west-dipping mylonitic shear zone along the western limb of the Bitterroot complex may provide a key for interpreting the postmylonitic structural evolution of the core complex. If this shear zone can be correlated to the Bitterroot mylonite zone to the east, then strong evidence for flexural uplift consistent with postmylonitic passage of a rolling hinge emerges.
机译：Bitterroot变质岩心复合体向东伸展伸展屋顶的岩石和地质年代学限制为比较伸展剥蚀早期阶段跨下盘壁的剥蚀速率提供了一种手段。西北和西南部Bitterroot变质岩心复合体中上层云状岩的U-Pb和〜（40）Ar /〜（39）Ar数据表明，大约在西下盘面被掘出到浅层（1-5公里）。 49 Ma，等温减压事件后，东部的下盘壁岩石仍处于高温状态，沿下盘壁西缘的表带上层铀的U-Pb年龄表明，带超群变质岩的阳极融化之间发生了多达13 km的顶顶在西下盘不迟于56 Ma处，并在ca附近安置了邻近的上隆Lolo温泉岩床。西北苦水根山脉49 Ma。在此间隔内的构造剥蚀作用从东下盘壁岩石中清除了大致相同量的上覆岩层，这表明平顶，东倾（30度至50度）的剪切带可能已经适应了顶棚的初始阶段。 〜（40）Ar /〜（39）Ar的冷却数据表明，西下盘墙的冷却与顶棚同步。相反，我们认为，在这个非屋盖阶段之后，东部下盘壁岩石的明显冷却延迟可能导致地热梯度略有增加。沿苦味根复合体西侧的西浸渍的绵状剪切带的暴露可能为解释该核心复合体的次炔属构造演化提供了关键。如果该剪切带可以与东部的苦根根斑岩带相关，那么就出现了与旋转铰链的次次木乃伊通行相一致的弯曲隆起的有力证据。

著录项

相似文献

  • 外文文献
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号