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首页> 外文期刊>Geological Society of America Bulletin >Timing of deformation and exhumation in the western Idaho shear zone, McCall, Idaho
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Timing of deformation and exhumation in the western Idaho shear zone, McCall, Idaho

机译：爱达荷州麦考尔西部爱达荷州剪切带变形和掘尸的时间

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摘要

The western Idaho shear zone is one of several Cretaceous high-strain zones in the Cordillera that are thought to have been associated with the northward translation and/or docking of terranes presently in British Columbia. Located in west-central Idaho, this zone of intense deformation consists of a mid-crustal exposure of a lithospheric-scale, intra-arc dextral shear zone that overprints the Salmon River suture zone along the western edge of the Idaho batholith. U/Pb zircon geochronology constrains the main phase of deformation to between ca. 105 and 90 Ma. Cessation of movement on the shear zone occurred by 90 Ma, as determined by dating of the syntectonic Payette River tonalite and a crosscutting pegmatite dike in the Little Goose Creek complex. The ~(40)Ar/~(39)Ar thermochronology indicates that the shear zone passed through both the hornblende (～550℃) and biotite (～325℃) closure temperatures between 85 and 70 Ma. The ~(40)Ar/~(39)Ar biotite dates from an outcrop-scale, crosscutting shear zone are indistinguishable from that of the host rock, indicating that deformation occurred above the closure temperature of biotite. Apatite fission-track analysis suggests that exhumation to shallow crustal levels occurred ca. 40 Ma during mid-Tertiary regional exhumation or renewed tectonic activity along the Salmon River suture zone. Taken together, the ~(40)Ar/~(39)Ar results and apatite fission-track analyses indicate a two-stage uplift history for the western Idaho shear zone. Overall, the geochronology indicates that dextral transpressional movement on the western Idaho shear zone was temporally distinct from the Early Cretaceous suturing event. Additionally, the first stage of exhumation recorded by the western Idaho shear zone immediately followed transpressional deformation. Cessation of displacement on the western Idaho shear zone by ca. 90 Ma indicates that the exhumation did not solely occur as a result of ductile deformation on the shear zone itself. Moreover, dextral strike-slip movement on the western Idaho shear zone had also ceased by 90 Ma, indicating that terrane translation models for the Cordillera can only use the western Idaho shear zone to accommodate northward translation up to ca. 90 Ma. Lastly, the timing of movement on the western Idaho shear zone and contractional deformation recorded in the Insular terrane suggests a correlation between these events. This hypothesis implies that the deformation recorded in the western Idaho shear zone may have been linked to the oblique collision of the Insular superterrane with North America.
机译：爱达荷州西部剪切带是科迪勒拉地区几个白垩纪高应变带之一，据认为与目前不列颠哥伦比亚省的地层北移和/或对接有关。该强烈变形区位于爱达荷州中西部，由岩石圈规模的弧内右旋剪切带的中壳暴露构成，覆盖了爱达荷岩基岩西缘的鲑鱼河缝合带。 U / Pb锆石的年代学将变形的主要阶段约束在ca左右。 105和90 Ma。剪切带上的运动停止发生在90 Ma，这由小鹅溪综合体中构造的Payette River孔雀石和横切伟晶岩堤的年代确定。 〜（40）Ar /〜（39）Ar的热年代学表明，剪切带同时通过了角闪石（〜550℃）和黑云母（〜325℃）的封闭温度，介于85Ma至70Ma之间。 〜（40）Ar /〜（39）Ar黑云母始于露头尺度的横切带，与母岩相差不大，表明变形发生在黑云母封闭温度以上。磷灰石裂变径迹分析表明，发掘到浅层地壳水平大约发生于大约3年。在第三纪区域发掘或沿鲑鱼缝合带重新构造活动期间40 Ma。综上，〜（40）Ar /〜（39）Ar结果和磷灰石裂变径迹分析表明，爱达荷州西部剪切带有两个阶段的隆升历史。总体而言，地质年代学表明，爱达荷州西部剪切带上的右旋压移运动在时间上不同于白垩纪早期缝合事件。此外，西部爱达荷州剪切带记录的掘尸第一阶段紧随压变之后。爱达荷州西部剪切带上的位移停止时间约为。 90 Ma表示发掘不仅是剪切区本身发生延性变形的结果。此外，在爱达荷州西部剪切带上的右旋走滑运动也已停止了90 Ma，这表明科迪勒拉山脉的地平移模型只能使用爱达荷州西部剪切带来适应向北平移，直到ca。 90毫最后，在爱达荷州西部剪切带上运动的时机和在Insular地层中记录的收缩变形表明这些事件之间存在相关性。该假设表明，爱达荷州西部剪切带记录的变形可能与Insular地层与北美的倾斜碰撞有关。

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