中—新生代东北和华北的洋陆转换作用

Ocean—continent transition process reveled by worldwide comparison of crust and upper mantle structures

本文对西太平洋的洋—陆转换作用进行探讨。西太平洋洋—陆转换带在中国东部可分为华南、华北—黄海和东北3个区段。东北地区中—新生代洋—陆转换作用涉及古今太平洋板块和蒙古—鄂霍茨克洋板块两方面俯冲作用的影响,产生大面积中基性岩浆和火山活动,从侏罗纪一直延伸到现在。不同于东北和华南地区,华北—黄海有克拉通型的岩石圈,在晚侏罗世—新近纪因为太平洋板块的大角度旋转造成软流圈低黏度物质上涌,和地壳拉张与幔源岩浆的底侵,造成上地壳裂谷型沉积盆地。燕山地区在侏罗纪与东北地区类似,有强烈的软流圈上涌和岩石圈岩石部分熔融,产生强烈岩浆活动。在白垩纪到新生代,因为蒙古—鄂霍茨克洋闭合和太平洋板块大角度旋转,发生沿蒙古—鄂霍茨克洋的转换断层的拉张,产生从南蒙古过锡林浩特的NW向玄武质岩浆和火山带。洋—陆转换带不同区段有不同的动力学作用演化过程,与先期岩石圈的性质、大洋板块俯冲带的分布、方向变化和俯冲持续时间、以及后期俯冲带后撤作用都有密切关系。洋—陆转换作用的统一后果是大陆的增生,但是不同区段大陆增生和物质运动的模式是不一样的。

This article discusses the ocean—continent conversion in the western Pacific Ocean regine. The Western Pacific ocean—continent Transition Zone by eastern China can be divided into three sections: South China, North China and Yellow Sea and Northeast China. The Mesozoic ocean—continent transition in Northeast China involved the influence of subduction in the ancient and modern Pacific Plates and the Mongolian—Okhotsk Ocean Plate, resulting in large areas of medium-to-basic magmatic and volcanic activities, extending from the Jurassic to the present. Different from the northeast and south China, the North China and Yellow Sea regine had a craton-type lithosphere in the Late Jurassic—Tertiary Period. The upwelling of low-viscosity material in the asthenosphere and the large-angle rotation of the Pacific plate caused the bottom the crustal tension and intrusion of mantle source magma, resulting in the upper crustal rift valley sedimentary basin. The Yanshan region was similar to the northeast region in the Jurassic, with strong asthenosphere upwelling and partial melting of lithospheric rocks, resulting in strong magmatic activity. In the Cretaceous to Cenozoic, because of the closure of the Mongol—Okhotsk Ocean and the large-angle rotation of the Pacific plate, there was a transform fault of the Mongol—Okhotsk Ocean stretching, resulting in NW basalt magma and volcanic belts passing through Xilinhot from Southern Mongolia. Different sections of the ocean—continent transition zone have different dynamic evolution processes, which are closely related to the nature of the early lithosphere, the distribution of the subduction zone of the oceanic plates, the direction change and the durations of the subduction, and the retreat of the late subduction zones. The common consequence of the ocean—continent transformation process was the accresion of continents, but the way of continental accresion and material movement in different segments were different.