燕山带中生代主要构造事件与板块构造背景问题

Major Mesozoic Tectonic Events in the Yanshan Belt and the Plate Tectonic Setting

对冀北、辽西火成岩体和火山岩的定年与野外构造的研究揭示,燕山地区主要缩短变形期为:①前中林罗期(180 Ma);②晚侏罗期(161～148 Ma);③早自垩期(143～127 Ma→117 Ma)。前中侏罗期的SN向缩短可能与蒙古弧—华北板块沿索伦缝合带拼合有关。晚保罗世—早白垩世的缩短变形可能是西伯利亚与蒙古—华北拼合板块沿其北1000～1800km外,蒙古—鄂霍茨克缝合带碰撞的板内响应。我国东部NNE向构造与岩浆的展布以及京北云蒙山区早白垩世向南的基底推覆和岩体侵人间密切的时空关联表明,它们遭受了与太平洋板块向西俯冲相关的热体制的影响。

Our field work and geochronologic studies in northern Hebei and western Liaoning areas indicate that the major Mesozoic contractional events in the Yanshan belt are of (1) pre-Middle Jurassic (Indosinian?) , (2) Late Jurassic and (3) Early Cretaceous age. The first N-S shortening could be a consequence of the collision of the Mongolian arcs along the Solon suture against the North China plate. Siberian-North China plate collision across the Jura-Cretaceous Mongo-lo-Okhotsk Sea more than 800-1000 km to the north could be responsible for the regional N-S intraplate contractional deformation in the Yanshan belt during Late Jurassic and Early Cretaceous time. The NNE-structural trends, the regional patterns of Mesozoic magmatism in eastern China and the close spatial and temporal ties existing in the middle crust between the S-directed Early Cretaceous basement nappe and voluminous plutonic intrusion suggest the results of the influence of thermal regimes resulting from the westward Pacific plate subduction and related magmatism.