松辽盆地北部深层火山岩剩磁特征与裂缝定向研究

A study on fracture orientation and characteristic of remnant paleomagnetization of deep-burial volcanic rocks, north of the Songliao Basin

系统的等温剩磁和热退磁分析表明,松辽盆地深层早白垩世火山岩具有特征剩磁和黏滞剩磁两组剩磁分量,载磁性矿物为磁铁矿.校正后的火山岩特征剩磁方向及古磁极位置与欧亚大陆的白垩纪古磁极位置,在95%置信区间内重叠,佐证了应用黏滞剩磁定向岩芯的方法是可行的.黏滞剩磁定向研究表明,研究区火山岩裂缝主要发育有北东向、北西向、近南北向和近东西向四组,其中北东向和北西向裂缝更占优势.古地磁定向成果与成像测井成果对比,显示出良好的定向效果.

Systematic analysis on isothermal remnant magnetization and thermal demagnetization displays that the deep-burial early Cretaceous volcanic rocks in the north of the Songliao Basin have two groups of stable remnant magnetization components comprising characteristic remnant magnetization and viscous remnant magnetization, with magnetite as the mineral carrying remanence. The direction of corrected characteristic remnant magnetization and its paleomagnetic pole are overlapping with those of synchronous Eurasia in the 95 % confidence range, which supports that it is reliable to apply viscous remnant magnetization in core orientation. The result of fracture orientation in volcanic rocks shows that there are four main groups of fracture in volcanic rocks with their trending in northeast, northwest, nearly north-south and nearly east-west. The former two groups are dominant. Orientation results resolved by the paleomagnetic method are confirmed by borehole image logging.