地球内部过程 Plate Tectonics Magnetismiii in Rocks--General Most iron-bearing minerals are at least weakly magnetic at surface temperatures Each magnetic mineral has a Curie居里 temperature, below which it remains magnetic, but above which it loses its magnetic properties. The Curie temperature varies from mineral to mineral, but it is always below the minerals melting temperature. A hot magma is therefore not magnetic, but as it cools and solidifies, and ferromagnesian 铁镁矿物 silicates and other iron-bearing minerals crystallize from it, those magnetic minerals tend to line up in the same direction. like tiny compass needles, they align themselves parallel to he lines of force of the earth's magnetic field, which run north-south, and they point to the magnetic north pole. They retain their internal magnetic orientation unless they are heated again. This is the basis for the study of paleomagnetism, fossil magnetism in rocks 环境迪顶学 minoucntalocelogu 真去率地球内部过程 • Plate Tectonics Magnetism磁 in Rocks—General： Most iron-bearing minerals are at least weakly magnetic at surface temperatures. Each magnetic mineral has a Curie居里 temperature, below which it remains magnetic, but above which it loses its magnetic properties. The Curie temperature varies from mineral to mineral, but it is always below the mineral’s melting temperature. A hot magma is therefore not magnetic, but as it cools and solidifies, and ferromagnesian 铁镁矿物 silicates and other iron-bearing minerals crystallize from it, those magnetic minerals tend to line up in the same direction. Like tiny compass needles, they align themselves parallel to the lines of force of the earth’s magnetic field, which run north-south, and they point to the magnetic north pole. They retain their internal magnetic orientation unless they are heated again. This is the basis for the study of paleomagnetism, “fossil magnetism” in rocks