松辽盆地白垩纪嫩江组黑色泥岩加热后磁性增强机制研究

发布时间：2018-09-02 05:31

【摘要】：磁化率随着温度的变化特征测量(κ-T曲线)可以用来确定磁性矿物类型及加热过程中的矿相变化。前人对松辽盆地松科1井南孔白垩系嫩江组一段上部至二段下部(972.46-1060.24m)的30个代表性样品进行了κ-T曲线测量,发现样品的磁化率值主要受控于顺磁性矿物,绝大部分样品的冷却曲线明显高于加热曲线,说明加热过程中有新的强磁性矿物生成,其居里温度在~500-560℃之间(李海燕等,2017)。但是,前人的研究未能确定新生成磁性矿物的类型,也未能确定该强磁性矿物来源于哪种矿物的转变,仅推测可能来自粘土矿物的高温段转化。基于此,本论文选择纯的粘土矿物、长石单晶和嫩江组样品开展了新的研究,以期揭示嫩江组黑色泥岩样品加热后磁性增强的机制。本论文对纯的粘土矿物、长石单晶和松科1井南孔代表性样品进行了磁化率随温度变化特征的测量(高、低温κ-T曲线)、粉晶X射线衍射实验(XRD)、扫描电镜观察(SEM)和能谱分析(EDS),取得了以下成果:1.纯的粘土矿物中,绿泥石和伊蒙混层样品的热稳定性较弱,加热后有新的强磁性矿物生成,磁化率值增大。其中,含菱铁矿的绿泥石样品因菱铁矿晶体中有Mg~(2+)和Mn~(2+)等离子,加热后生成锰铬铁矿,其居里温度为~520℃。蒙脱石和高岭石样品的热稳定性强,其κ-T曲线的加热曲线和冷却曲线基本可逆,未见明显的矿相转变。2.纯的长石单晶颗粒的热稳定性强,其κ-T曲线的加热曲线和冷却曲线基本可逆,未见明显的矿相转变。但绿泥石化长石单晶颗粒和弱风化的钾长石单晶颗粒的热稳定性较弱,加热后有少量磁铁矿生成,磁化率值增大。3.在氩气环境下的加热过程中,当加热温度高于~350℃时,嫩江组黑色泥岩样品的磁性增强。该磁性增强来源于样品在加热过程中发生的矿相转变,推测其过程为:在石英的参与下,伊利石、高岭石等粘土矿物与含铁、镁的矿物反应,转变为云母、微量磁铁矿和较多的含Mg/Mn的磁铁矿。其中,含Mg/Mn的磁铁矿的居里温度为~520℃。4.在氩气环境下的加热过程中,嫩江组黑色泥岩样品中的黄铁矿在热处理过程中转变为反铁磁性的六方磁黄铁矿,对其加热过程中的磁性增强没有明显影响。
[Abstract]:The characteristic measurement of magnetic susceptibility with temperature (魏 -T curve) can be used to determine the type of magnetic minerals and the change of mineral phases during heating. Thirty representative samples (972.46-1060.24m) from the upper part to the lower part (972.46-1060.24m) of the first member of the Cretaceous Nenjiang formation in the south hole of Songke-1 well in Songliao Basin were measured. It was found that the magnetic susceptibility of the samples was mainly controlled by paramagnetic minerals. The cooling curves of most of the samples were obviously higher than those of the heating curves, indicating that new strong magnetic minerals were formed during heating, and their Curie temperature ranged from 500 鈩，

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