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西北地区(贺兰山——六盘山以西、昆仑山——秦岭以北)主要受南北挤压力和南北对扭力作用,产生了以北西向的西域系和东西向的纬向系为主干的多构造体系的复合。形成了与我国东部截然不同的区域构造特征。 1.地壳结构: 莫霍面一般为36—60公里;地幔上隆部位常常是中新生代厚度变化的斜坡带上。 2.区域构造格架: (1)西域系:由阿尔泰构造带、博罗霍洛——祁连构造带及巴楚——奇曼塔克构造带等为骨干和相应的沉降带所组成。发生于早古生代,晚古生代活动最强烈,中新生代仍有活动。
Northwest China (Helan Mountain-west of Liupan Mountain, Kunlun Mountains-north of Qinling Mountains) is mainly affected by north-south compression and north-south torsional forces, resulting in a multi-tectonic structure dominated by the NWWS and the east-west zonal system Complex system. Formed a distinctive feature of regional tectonics in eastern China. 1. Crustal structure: The Moho is generally 36-60 km; the upper mantle uplift is often the mid-Cenozoic thickness gradient slope belt. 2. Regional tectonic framework: (1) The Western Division is composed of Altai structural belt, Boluo Holuo-Qilian tectonic belt and Bachu-Qimen Takeda tectonic belt, which are the backbone and corresponding subsidence belts. Occurred in the Early Paleozoic, the Late Paleozoic was the strongest activity, the Mesozoic and Cenozoic still activities.