青藏高原新生代造山带与伊比利亚古生代造山带壳内强反射的岩石组成成因研究

Although strating time about block construct mechanism is dispute,orogen is being from Paleozoic. The difference between Paleozoic orogen and Neozoic orogen structure has long been a subject of interest to Earth scientists..There are strong reflective body at Tibet Neozoic orogen and Iberia Palezoic orogen,but the formation is disputed.Estimates of the composition of Earth's crust is important because such a model is critical to understanding the growth and evolution of the continents, We propose a joint scheme (chain constrain technique) by combing all available constrains to reduce the non-uniqueness in mapping rock distribution. The origin of strong crustal reflectors in vertical incidence reflection seismic profiles is generally attributed to either rock layering in the form of bedding or metamorphically segregated lithologies, deformation fabrics in shear zones, fluids, or igneous intrusions。Clearly, the cause of the reflectivity is a change in physical properties between the reflector and the surrounding rock. Therefore, further constraints can be placed on the nature of a reflector if potential field data (in particular gravity and heat flow) together with P-wave (Vp) and S-wave (Vs) data from wide-angle or refraction seismic data are available. Even tighter control on the nature of a crustal reflector can then be obtained by the comparision of rock physical properties measured in-situ via potential field and seismic methods with seismic velocities and densities measured in laboratory experiments. We get synthetic vertical incidence seismic reflection section using reflectivity method, we hope this method is effective for crustal composition.

尽管人们对于板块构造机制作用的起始时间争论不一，古生代以来造山带的存在是不争的事实，古生代与新生代造山带内结构构造有何异同是地球科学界关注的热点问题之一。现有研究表明青藏高原新生代造山带与伊比利亚古生代造山带壳内均存在强反射带，但其成因还有争论。大陆地壳岩石组成结构的研究能够为大陆形成、演化提供重要信息，利用多种地球物理参数来确定岩石类型，能有效减少岩石组成的多解性。深反射地震资料中的强反射体可能成因有岩石成层、剪切带的剪切形变或者火成岩入侵，对反射体成因的研究能够为认识地壳的不同演化模式提供新的信息。在已有的重建地壳岩石组成结构方法的基础上，通过采集研究区出露岩石样品，进行实验室测量获取岩石样品的相关参数，利用反射率法对不同岩石样品组合计算合成地震记录，和实际资料的强反射特征进行对比，对强反射体内的岩石组成进行进一步推断。

大陆地壳岩石组成结构的研究能够为大陆形成、演化提供重要信息，利用多种地球物理参数来确定岩石类型，能有效减少岩石组成的多解性。本项目利用综合地球物理参数重建地壳岩石组成结构。通过链式约束的方法，构建了INDEPTH Ⅲ剖面的地壳岩石组成模型。从构建的岩石组成模型可以看出，班公怒江缝合带两侧岩石成分有明显差异。IBERSEIS，是一条位于西班牙西南部的剖面，这条剖面穿过三条主要的构造阶地。我们构建了IBERSEIS 剖面的地壳岩石组成结构。采集出露地表的岩石样品，计算反射系数来测试它们是否接近与高反射体的深反射资料的结果。我们用反射率法计算不同岩石样品组成的合成地震记录。实验结果表明，以前对于IBERSEIS反射体的解释为有一个铁镁质的岩床是非常合理的，它的形成很可能是滑脱构造带铁镁质岩浆的侵入。在已有的重建地壳岩石组成结构方法的基础上，通过采集研究区出露岩石样品，进行实验室测量获取岩石样品的相关参数，利用反射率法对不同岩石样品组合计算合成地震记录，对强反射体内的岩石组成进行进一步推断。