山东胶莱盆地鲁科一井上白垩统火山岩的岩石磁学和磁组构研究

Rock magnetism and magnetic fabrics of upper Cretaceous volcanic rocks from CCSD-LK-I,in Jiaolai Basin,Shandong province

通过对山东胶莱盆地鲁科一井钻孔上白垩统上、下火山岩进行岩石磁学研究,确定上火山岩的载磁矿物为粒径较细的假单畴磁铁矿,部分样品含赤铁矿;下火山岩的载磁矿物为粒径较粗的假单畴磁铁矿,大部分样品含赤铁矿,少量样品的载磁矿物以赤铁矿为主.磁化率各向异性结果显示,火山岩样品的磁化率各向异性度较低(1.002<P_j<1.209),磁面理大于磁线理,磁化率最大轴接近平行于水平面分布,最小轴接近垂直于水平面分布.这些结果说明火山岩样品保存了原始岩浆流动磁组构特征,并暗示火山岩地层接近水平.以上结果表明该钻孔上白垩统火山岩适合于古地磁和古强度研究.

We report rock magnetism and anisotropy of magnetic susceptibility（ AMS） studies on the upper Cretaceous volcanic rocks from the Cretaceous Continental Scientific Drilling borehole in the Jiaolai Basin（ CCSD-LK-I）, Shandong province. Rock magnetic experiments include temperature-dependence of magnetic susceptibility, acquisition of isothermal remanent magnetization（ IRM） and its demagnetization,and hysteresis loops. Results indicate that the upper volcanic rocks are dominated by finer pseudo single domain（ PSD） magnetite; and the lower volcanic rocks are dominated by coarse PSD magnetite and most samples contain hematite,with a small amount of samples dominated by hematite.AMS experiments show that volcanic rock samples show low degree of anisotropy of magnetic susceptibility（ 1. 002 〈Pj 〈1. 209） and the magnetic foliation is more obvious than magnetic lineation,which indicate a primary magma flow fabric. The maximum anisotropy axes are nearly parallel to the horizontal plane and the minimum anisotropy axes are nearly perpendicular to the horizontal plane,which imply horizontal strata. Those characteristics suggest that the upper Cretaceous volcanic rocks in the Jiaolai Basin are promising for paleomagnetism and paleointensity studies.