Formation of magnetic minerals at hydrocarbon-generation conditions
Formation of magnetic minerals at hydrocarbon-generation conditions
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DOI：
10.1016/j.marpetgeo.2015.10.003
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发表时间：
2015-12
影响因子：
4.2
通讯作者：
R. Abubakar;A. Muxworthy;M. Sephton;P. Southern;J. Watson;A. Fraser;T. Almeida
中科院分区：
文献类型：
--
作者：
R. Abubakar;A. Muxworthy;M. Sephton;P. Southern;J. Watson;A. Fraser;T. Almeida
本文报道了英格兰南部多塞特郡威塞克斯盆地三个烃源岩样品中磁性矿物的热解和形成过程。室内实验条件再现了生油岩的次生环境。在室温和极低温度（5 K）下对加热和未加热样品进行的磁性分析，加上透射电子显微镜成像和X射线分析，揭示了纳米尺寸（<10 nm）的磁性颗粒的形成，这些颗粒在所分析的岩石样品中变化，但更重要的是在热解温度范围内变化。磁性测量表明，所有岩石样品的磁性矿物的形成在250 °C时达到峰值，然后在300 °C时下降，然后在320 °C时再次上升。新形成的磁性矿物被认为主要是磁黄铁矿，虽然磁铁矿和云英岩也被认为是存在的。形成的磁性矿物的大小表明与石油一起迁移的倾向，这可能解释了在油田上方和油田内部观察到的磁性异常。
In this paper, we report the pyrolysis and formation of magnetic minerals in three source rock samples from the Wessex Basin in Dorset, southern England. The experimental conditions in the laboratory recreated the catagenesis environment of oil source rocks. Magnetic analysis of both the heated and the unheated samples at room temperature and at very low-temperatures (5 K), coupled with transmission electron-microscopy imaging and X-ray analysis, revealed the formation of nanometre-sized (<10 nm), magnetic particles that varied across the rock samples analysed, but more importantly across the pyrolysis temperature range. Magnetic measurements demonstrated the formation of these magnetic minerals peaked at 250 °C for all rock samples and then decreased at 300 °C before rising again at 320 °C. The newly formed magnetic minerals are suggested to be primarily pyrrhotite, though magnetite and greigite are also thought to be present. The sizes of the magnetic minerals formed suggest a propensity to migrate together with oil potentially explaining the magnetic anomalies observed above and within oil fields.