辽西阜新-义县盆地及附近地区早白垩世地壳大规模减薄及成因探讨  

Early Cretaceous Large-scale Crustal Thinning in the Fuxin-Yixian Basin and Adjacent Area in Western Liaoning

作　　者：张宏[1] 柳小明[1] 李之彤[2] 杨芳林[2] 王晓蕊[1] 

机构地区：[1]西北大学地质系 [2]沈阳地质研究所,110032

出　　处：《地质论评》2005年第4期360-372,共13页Geological Review

基　　金：本文为科技部2000年度科技基础性工作第35专项;国土资源部专项(编号9501122-3)中国地质调查局项目(编号200113000052-2)的研究成果。

摘　　要：辽西阜新-义县盆地及其附近地区,其早白垩世的地层、构造和火山岩有明显的特殊性。在地层方面,阜新-义县盆地内下白垩统分布较齐全,而土城子组及以前的侏罗系基本缺失,反映在义县期之前,阜新-义县盆地处在剥蚀环境中(正地形),而在早白垩世处在快速沉降的沉积环境中(负地形),并在早白垩世沉降了约7 km。构造方面,晚侏罗世末期,褶皱、逆冲作用反映研究区发生了一定规模的挤压抬升作用;早白垩世阜新-义县盆地的伸展断陷作用贯穿始终,也说明了该地区早白垩世快速沉降的存在。在火山岩方面,阜新-义县盆地及附近地区的义县组下部多处分布有含镁较高的火山岩,其地球化学特征反映该火山岩岩浆源于地幔,同时有复杂的成因,这提供了阜新-义县盆地及附近地区早白垩世地壳大规模减薄、地幔岩浆上涌的信息。以上地质特征说明,早白垩世阜新-义县盆地发生了与地幔作用有关的大规模地壳减薄作用。The strata, tectonics and geochemistry of volcanic rocks in the Early Cretaceous of the Fuxin--Yixian Basin and adjacent area in western Liaoning have some special features. Stratigraphically, the Lower Cretaceous is continuous and complete, but the Jurassic is nearly absent, which reflect that the basin was in a denudation setting before the Yixian period （Jurassic）, and was fast subsiding in the Early Cretaceous with a total subsidence of about 7000m. Tectonically, in the Early Cretaceous, extensional faulting kept on, while, at the end of the Late Jurassic, folding and thrusting indicated compression and uplifting. Geochemically, high-Mg basalts in the lower Yixian Formation suggest that they are from the mantle with a complex magma source, which shows a large-scale crustal thinning and uprising of mantle magma in the Early Cretaceous. The above geological characteristics reflect that the crustal thinning in the Early Cretaceous had a direct relationship with mantle process and lithospheric thinning. These results are important to further study of the regional background of the volcanic rocks of the Yixian Formation, magmatism, and the cause of lithospheric thinning in eastern China.

关 键 词：辽西阜新-义县盆地 白垩世 地壳运动 沉积环境 地壳减薄作用 地质条件 地层接触关系 

分 类 号：P534.53[天文地球—古生物学与地层学]