Transient thermal regimes in the Sierra Nevada and Baja California extinct outer arcs following the cessation of Farallon subduction
Transient thermal regimes in the Sierra Nevada and Baja California extinct outer arcs following the cessation of Farallon subduction
复制标题
法拉隆俯冲停止后，内华达山脉和下加利福尼亚州外弧灭绝的瞬态热状况
DOI：
--
复制
发表时间：
2009
期刊：
影响因子：
--
通讯作者：
D. Blackwell
中科院分区：
文献类型：
--
作者：
K. Erkan;D. Blackwell
[1]我们研究的热弛豫的内华达州和下加利福尼亚灭绝外弧块的Farallon俯冲下北美西部的逐步停止开始在2030马。这两个地区在地质、地貌、刚体行为和相对较低的地震活动性方面表现出许多相似之处。在热模型中，我们结合联合收割机不同的地球物理和地球物理研究的结果，以限制俯冲停止前的外弧的热状态和几何形状，然后使用构造重建的结果在这些地区模拟俯冲后的温度响应。一个约束良好的区域热模型，这些块体使用的许多早期的研究结果在这些地区证实，目前在这些地区的低热流值是非常冷的外弧俯冲带的热制度的残余，甚至长达30马后停止俯冲。因此，北美板块的整个太平洋边界仍然处于短暂的热状态。计算出的内华达州和半岛地块的岩石圈低温与大地测量研究中获得的刚体行为以及地震学研究中获得的孕震层厚度非常相关。这与这两个地区都被北美西部板内和板外运动引起的强烈变形所包围的事实相反。这些低温岛在现今北美板块和太平洋板块的相互作用中起着重要的作用，并对转换边界的广泛变形做出了贡献。熄灭的外弧的热松弛包括垂直加热从下面的软流圈和横向加热从熄灭弧后（盆地和山脉），这仍然是一个高热流区后，俯冲停止。我们认为，来自Sierra内华达州的盆地和山脉（以及自205 Ma以来来自半岛地块的加州湾扩张中心）的显著侧向热传递可能是沿着死火山弧的俯冲后火山/岩浆活动和Sierra内华达州地块近期倾斜隆升的主要驱动机制。Sierra内华达州地区岩石圈温度低也可以解释Sierra内华达州南部地幔岩石圈下涌的高地震速度。
[1] We examine the thermal relaxation of the Sierra Nevada and Baja California extinct outer arc blocks following the progressive cessation of Farallon subduction under western North America beginning at ∼30 Ma. Being parts of the same outer arc until the inland jump of the San Andreas transform fault at ∼5 Ma, these two regions show many similarities in their geology, geomorphology, rigid body behavior, and their relatively low seismicity. In the thermal model, we combine results of different geophysical and geophysical studies to constrain the thermal state and geometry of the outer arcs before the cessation of subduction and then model the postsubduction temperature responses in these regions using the results of the tectonic reconstructions. A well-constrained regional thermal model of these blocks using the results of many earlier studies in these regions confirms that the present low heat flow values in these regions are the remnants of the very cold outer arc thermal regime of the subduction zone even as long as 30 Ma after cessation of subduction. Thus the entire Pacific boundary of the North American plate is still in a transient thermal state. The calculated low lithospheric temperatures in the Sierra Nevada and Peninsular blocks correlate very well with their rigid body behavior obtained from geodetic studies, and seismogenic layer thicknesses obtained from seismological studies. This is in contrast with the fact that both regions are surrounded by intense deformation associated with the western North America intraplate and extraplate motions. These low-temperature islands play important roles in the present interaction of the North American and Pacific plates and contribute to the broad deformation of the transform boundary. The thermal relaxation of the extinct outer arcs includes both vertical heating from the underlying asthenosphere and the lateral heating from the extinct back arc (Basin and Range), which has remained as a high heat flow region after the cessation of the subduction. We suggest that the significant lateral heat transfer from the Basin and Range in the Sierra Nevada (and from the Gulf of California spreading center in the Peninsular block since ∼5 Ma) may be the main driving mechanism of the postsubduction volcanism/magmatism along the extinct volcanic arc and the recent tilted uplift of the Sierra Nevada block. The low lithospheric temperatures in Sierra Nevada region may also explain the observation of the high seismic velocities in the mantle beneath the southern Sierra Nevada where the downwelling of the mantle lithosphere proposed.