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磁化率值不仅受控于天然岩石和环境物质中磁性颗粒的组合特征,还与实验室内的处理过程有关,包括热处理过程和加场处理过程。热处理过程通常改变磁性矿物的类型,使样品的磁化率值发生明显变化,因而备受关注。但加场处理过程对样品磁化率的影响在于改变其中所含磁性颗粒的磁畴结构,这种变化是微观的,目前尚未受到应有的重视。本文选择8块泥岩样品进行了加场处理对其磁化率影响的研究。样品取自松辽盆地松科1井青山口组一段,主要携磁矿物为准单畴(PSD)或多畴(MD)磁铁矿。在逐步获得等温剩磁直至饱和的过程中,逐步测量样品的磁化率值。随后对其进行单轴系统交变退磁,逐步测量剩磁后,完成磁化率测量。结果发现:1)直流场使样品的磁化率值增大。在低于50mT的外加场中,随外加场的增强,样品的磁化率值快速增大;之后,随外加场的增强,样品的磁化率值基本不变,直到600mT;600mT～1T之间样品的磁化率值又大幅增大;最终,样品的磁化率较初始值(x_0)增大0.84%～3.40%。这种磁化率值的增大受控于样品内PSD或MD磁铁矿磁畴结构的改变,与磁铁矿的含量无关。2)样品获得SIRM后进行的逐步交变退磁使其磁化率值有所降低,随交变场的增强,其降低的幅度也增大,但是,交变场达到100mT时,样品的磁化率值仍较x_0高。经逐步交变退磁后,样品的磁化率较x_0增加0.03%～2.42%。因而,大然样品在进行磁化率测量之前,不能将其置于任何直流场或交变场中处理。
Magnetic susceptibility values are not only controlled by the combination of magnetic particles in natural rocks and environmental substances, but also related to laboratory processes, including heat treatment and addition. Heat treatment process usually changes the type of magnetic minerals, so that the magnetic susceptibility value of the sample changes significantly, so much attention. However, the effect of adding field process on the magnetic susceptibility of the sample is to change the magnetic domain structure of the magnetic particles contained therein. Such change is microscopic and has not been given due attention at present. In this paper, 8 samples of mudstone were selected to study the influence of adding field on the magnetic susceptibility. The samples were taken from the first member of the Qingshankou Formation of Songke-1 well in Songliao Basin, and mainly carry the magnetic minerals as quasi-single domain (PSD) or multi-domain (MD) magnetite. The magnetic susceptibility value of the sample is measured step by step in the course of obtaining isothermal remanence until saturation. Subsequently, the uniaxial alternating demagnetization was carried out and the remanent magnetization was measured gradually to complete the magnetic susceptibility measurement. The results show that: 1) DC field increases the susceptibility of the sample. In the applied field below 50mT, the magnetic susceptibility increases rapidly with the increase of applied field. After that, the magnetic susceptibility of the sample remains unchanged with the increase of applied field until 600mT and 600mT ~ 1T The magnetic susceptibility increased sharply. Finally, the magnetic susceptibility of the sample increased by 0.84% ~ 3.40% from the initial value (x_0). This increase in susceptibility values is governed by changes in the domain structure of the PSD or MD magnetite in the sample, regardless of magnetite content. 2) After the sample is SIRM, the magnetic susceptibility of the samples decreases gradually with the increase of the alternating field, but the decreasing range of the samples decreases with the increase of the alternating field. However, when the alternating field reaches 100mT, the susceptibility Still higher than x_0. After gradual alternating demagnetization, the magnetic susceptibility of samples increased by 0.03% ~ 2.42% compared with x_0. Therefore, the macroscopic sample can not be placed in any DC field or alternating field before magnetic susceptibility measurement.