Constraints on Large-Magnitude Extension Coupled to Subduction Channel Flow Above a Flat Slab Segment - Southern Sierra Nevada Region, California

与平板段上方俯冲通道流耦合的大范围伸展的约束 - 加利福尼亚州内华达山脉南部地区

• 批准号: 0739071
• 负责人: Jason Saleeby
• 金额: $ 20.83万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-01-15 至 2011-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0739071&HistoricalAwards=false
• 关键词: Constraints; Large; Magnitude; Extension; Coupled

Buoyancy contrasts between oceanic lithosphere and continental lithosphere may lead to subduction, the driving of the oceanic plate below the continental plate. This process of subduction is common around our planet and it is expressed as, for example, the Pacific Rim of Fire. It is called this due to the chains of volcanoes that outline the Rim. Another consequence of subduction is extensive seismicity or earthquake energy release. In order to understand the evolution of subduction regimes it is critical for basic research into the geometric evolution of the continental crust to continue. This research is at the cutting edge of the field of tectonics, with indirect implications for volcanism, earthquake hazard mitigation, genesis of metallic ores, and thermal and fluid distribution in the crust. Unless we understand the geometric evolution of the Earth at depth we will never fully understand the processes that control these issues.Oceanic lithosphere subducts beneath continental lithosphere along a variety of trajectories, generally characterized as steep, shallow, or flat. About ten percent of Earth's subduction zones consist of extensive shallowly dipping or flat subducted slabs, indicating the tectonic removal of mantle lithosphere forming the base of the continent. Overriding continental plate orogens in such cases possess zones of intensified crustal shortening and gaps in arc magmatism. Shallow subduction zone segments are also known to steepen with time, but the geological consequences of such steepening are poorly understood. The fact that the remnants of shallow and flat subduction zones are so rarely recognized in ancient orogens suggests that the tectonic processes attendant in their complete life cycle disrupt the crust to such a state that the defining characteristics are lost. In the southern Sierra Nevada-Mojave Desert an ~500 km long segment of the Cretaceous active margin has been shown to have experienced the complete life cycle of a shallow slab segment in the Farallon plate. There is evidence indicating that during the demise of this shallow slab segment large magnitude extension deformed the overriding plate. It also appears that material subducted along that shallow trajectory rapidly ascended back out the upper levels of the subduction zone, coupling extensional strain into the overriding plate. This study employs geologic mapping and structural analysis, petrography, microfabric analysis, thermobarometry, and geochronology to quantify the amount of overriding plate extension, and to determine the strain, displacement and thermal history of the underlying subduction assemblage.

海洋岩石圈和大陆岩石圈之间的浮力对比可能导致俯冲，这是大陆板下方的海洋板的驱动。 这种俯冲过程在我们的星球周围很普遍，它表示为例如太平洋的火rim。 这是由于概述边缘的火山的链条而称之为。 俯冲的另一个结果是广泛的地震或地震能量释放。 为了了解俯冲制度的演变，对于大陆地壳的几何演化而言，至关重要的是继续。 这项研究处于构造领域的最前沿，对火山主义，减轻地震危险，金属矿石的起源以及地壳中的热和流体分布具有间接影响。 除非我们了解地球在深度上的几何演化，否则我们将永远不会完全理解控制这些问题的过程。沿多种轨迹的大陆岩石圈下方的岩石圈支板沿多种轨迹，通常以陡峭，浅层或平坦为特征。地球俯冲带的大约百分之十，由广泛的浅浸出或平坦的俯冲板组成，表明构造了岩层岩石圈的构造，形成了大陆的底部。在这种情况下，覆盖大陆板牛根具有加剧的地壳缩短区域，并且在弧岩浆中具有差距。较浅的俯冲带段也随着时间的流逝而陡峭，但是这种陡峭的地质后果知之甚少。在古老的牛根中很少认识到浅层和平坦的俯冲带的残余物，这表明，整个生命周期中服务的构造过程破坏了地壳，以至于丢失了定义特征。在内华达州塞拉山脉南部，沙漠中有大约500公里长的白垩纪活跃边缘长500公里，已显示出在法拉隆板块中经历了浅层平板段的完整生命周期。有证据表明，在此浅平板段的消亡过程中，大尺寸的延伸幅度大变形。看来，沿浅轨迹的俯冲迅速升至俯冲带的上层，将伸展应变耦合到覆盖板中。 这项研究采用地质映射和结构分析，岩石摄影，微型实物分析，热量计量学和地质学来量化压层板扩展的量，并确定基础俯冲组合的应变，位移和热历史。