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俯冲隧道是指在会聚板块边缘、俯冲板片与上覆板片之间的剪切带及其中发生运动的物质,这些物质在俯冲隧道中经历了复杂的温度、压力、应力和应变等的演化以及流体和熔体的作用,而后部分物质可以从>100 km的深度处折返至地表,从而形成自然界中出露的高压-超高压变质岩带.动力学数值模拟是定量化的研究该俯冲隧道过程的重要手段,前人的研究大多基于热动力学模型,但是一般不包含流体的活动和影响,因此上覆岩石圈物质很少参与到俯冲隧道过程中,这些模型与地质概念模型之间尚存较大差异.本文采用了新的包含流体-熔体活动的数值模型,对俯冲隧道的精细过程进行模拟研究.结果表明,俯冲隧道中的物质既包含了从俯冲板块拆离的表壳岩,也包含了从上覆板块刮擦、蚀变的地幔岩,从而形成一个构造混杂岩体.在特定条件下,俯冲隧道中的混杂岩既可近垂直向上穿过地幔楔侵入上覆地壳中,亦可近平行于俯冲隧道斜向上折返,形成靠近缝合带的高压-超高压变质岩.基于该数值模型及前人的地质概念模型,首先对大洋俯冲隧道和大陆俯冲隧道的特征进行了细致的对比和总结.而后,又对含水模型与无水模型进行了对比,主要区别在于无水模型中由于缺少流体-熔体活动而产生的弱化作用,上覆岩石圈的变形很小,在俯冲隧道过程中的参与程度也很低.最后,对数值模型中的一个重要的边界条件,即板块会聚速率,进行数值模拟研究.结果表明快速会聚导致上覆岩石圈剧烈变形,造山带主要沿上盘单侧生长;相反,在慢速会聚条件下,上覆岩石圈变形较小,造山带主要沿下盘单侧生长;而在中等会聚速率下,造山带沿上盘、下盘同时生长.
Subduction tunnels refer to the shear bands and the materials that move between the subducting slab and the overlying slab at the edge of the converging plate. These subducts undergo complex temperature, pressure, stress and strain evolutions in subducted tunnels As well as fluids and melts, and some of the material can then be returned to the earth’s surface at depths> 100 km to form a naturally occurring high-pressure-ultrahigh-pressure metamorphic belt. Numerical simulation of the dynamics is a quantitative study of the subducted tunnel Most of the previous studies are based on the thermodynamic model, but generally do not include the fluid activity and influence. Therefore, the overlying lithosphere is rarely involved in the subduction tunnel. The relationship between these models and the geological conceptual model Which is quite different.This paper uses a new numerical model including fluid-melt activity to simulate the subtle process of subduction tunnel.The results show that the subduction tunnels contain both the surface rock , But also the mantle rocks that have been scraped and altered from the overlying plate to form a tectonic mélange. Under certain conditions, melanges in the subducted tunnels are both accessible Vertically up through the mantle wedge into the overlying crust, and can also be folded back parallel to the oblique direction of the subducted tunnel to form high-pressure-ultrahigh-pressure metamorphic rocks close to the suture zone.Based on the numerical model and the predecessor’s geological conceptual model, Subducted tunnels and continent subduction tunnels were compared and summarized in detail.And then, the comparison between water-containing model and water-free model was made, the main difference was the weakening effect of water-free model due to the lack of fluid-melt activity, The deformation of the overlying lithosphere is very small and the participation in the subduction tunnel is also very low.Finally, numerical simulation is conducted on an important boundary condition in the numerical model, namely the plate convergence rate.The results show that the rapid convergence leads to a On the contrary, under the condition of slow convergence, the deformation of the overlying lithosphere is small, and the orogenic belt mainly grows along one side of the lower plate. At moderate convergence rate, Orogenic belt along the plate, under the plate while growing.