胶东半岛黄崖剖面早白垩世火山岩古地磁结果及其构造意义  

Paleomagnetism of Early Cretaceous volcanic rocks at Huangya section in Jiaodong Peninsula and implications for tectonics

作　　者：秦华峰[1] 潘永信[1] 贺怀宇[1] 杨列坤[1] 朱日祥[1] 

机构地区：[1]中国科学院地质与地球物理研究所古地磁与地质年代学实验室,北京100029

出　　处：《岩石学报》2016年第10期3205-3213,共9页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(91414101;41210003)资助

摘　　要：对采自于胶东半岛黄崖剖面火山岩样品进行了系统的岩石磁学和古地磁学研究,结果表明HY1和HY2熔岩流样品的载磁矿物主要为磁铁矿和赤铁矿的混合,HY3熔岩流的样品主要为磁铁矿。系统热退磁实验从40块样品中分离出了稳定的特征剩磁方向,获得古地磁偏角/倾角平均方向为12.8°/62.4°(α95=4.8°),对应的平均虚地磁极位置为76.7°N/162.6°E(A95=6.2°)。40Ar/39Ar同位素定年结果显示,HY3火山岩的喷出年龄约为115.3±1.3 Ma^115.6±1.6 Ma(2σ)。比较结果显示,未发现研究区相对于华北块体在早白垩世有较大幅度的旋转或位移。对比山东、辽宁地区以及朝鲜半岛南部已有的晚中生代古地磁数据,发现侏罗-白垩纪期间古地磁的偏角随时间变化规律具有相似性,说明块体的旋转运动具有较一致规律性,指示东亚东缘构造运动可能受到古太平洋俯冲运动方向调整的影响。Rock magnetism and paleomagnetism study was conducted on 42 volcanic rock samples collected from 3 sites at Huangya section in Jiaodong Peninsula,Shandong Province in eastern China.Stepwise thermal demagnetization on 40 samples yielded stable characteristic remanent magnetization（ ChRM） directions.Their overall average direction is D/I = 12.8 °/62.4 °（ α95= 4.8 °） with a corresponding average virtual geomagnetic pole（ VGP） at 76.7 ° N and 162.6 ° E（ A95= 6.2 °）.The40 Ar/39 Ar age of HY3 is about between 115.3 ± 1.3 Ma and 115.6 ± 1.6 Ma（ 2 σ）.It indicates that the sampling area has no significant rotation and displacement relative to the North China Block（ NCB） in the Early Cretaceous.When comparing to available paleomagnetic data of Late Mesozoic we found that Shandong and Liaoning regions from Late Jurassic to the end of Cretaceous shows similar pattern of declination variation with time.It suggests that that the tectonic activity in eastern NCB was likely affected by the subduction process of paleo-Pacific plate during Cretaceous time.

关 键 词：古地磁 早白垩纪 胶东半岛 构造旋转 火山岩 

分 类 号：P318.44[天文地球—固体地球物理学] P588.144[天文地球—地球物理学]