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

大洋岩石圈和大陆岩石圈之间的浮力差异可能导致大洋板块向大陆板块下方俯冲。 这种俯冲过程在我们的星球上很常见，它被表达为，例如，环太平洋火山。 它之所以被称为这个，是因为火山链勾勒出了边缘。 俯冲的另一个后果是广泛的地震活动或地震能量释放。 为了了解俯冲体制的演变，继续对大陆地壳的几何演变进行基础研究至关重要。 这项研究处于构造学领域的前沿，对火山作用、地震减灾、金属矿的成因以及地壳中的热和流体分布有间接影响。 除非我们了解地球在深度上的几何演化，否则我们永远不会完全理解控制这些问题的过程。大洋岩石圈向大陆岩石圈之下沿着各种轨迹俯冲，一般具有陡、浅或平的特征。大约10%的地球俯冲带由广泛的浅倾或平坦的俯冲板片组成，表明地幔岩石圈的构造移动形成了大陆的基础。在这种情况下，上覆大陆板块造山带具有地壳缩短加剧的区域和弧岩浆活动的空隙。浅俯冲带段也被称为陡峭的时间，但这种陡峭的地质后果知之甚少。浅而平坦的俯冲带的残余在古代造山带中很少被发现，这一事实表明，伴随着它们整个生命周期的构造过程将地壳破坏到这样一种状态，以至于定义特征消失了。在内华达山脉-莫哈韦沙漠南部，一段约500 km长的白垩纪活动边缘已被证明经历了法拉隆板块浅板段的完整生命周期。有证据表明，在这个浅板段消亡期间，大幅度的伸展使覆盖板块变形。此外，似乎物质俯冲沿着浅轨迹迅速上升回俯冲带的上层，耦合到覆盖板块的拉伸应变。 本研究采用地质测绘和结构分析，岩相学，微组构分析，热压，和地质年代学，以量化覆盖板块的伸展量，并确定应变，位移和热历史的基础俯冲组合。

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.