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通过对中国大陆科学钻探工程主孔花岗质片麻岩进行详细的岩石磁学研究及岩石矿物学分析表明:花岗质片麻岩磁化率(0.570×10-7~120.450×10-7 m3·kg-1,平均29.996×10-7 m3·kg-1)在主孔所有岩石中仅次于蛇纹石化石榴石橄榄岩,而其天然剩余磁化强度(0.002×10-3~2.109×10-3 Am2·kg-1,平均0.210×10-3 Am2·kg-1)则是所有岩性中最低的.磁化率随温度变化曲线、交变退磁曲线及磁滞回线特征表明,花岗质片麻岩中磁性矿物组合主要成分为磁铁矿,小部分样品中含有赤铁矿,其中磁铁矿以多畴为主,伪单畴磁铁矿仅在少量样品中出现.和同为完全退变质岩的角闪岩(完全退变质榴辉岩)相比,花岗质片麻岩具有相似的磁性矿物组合,但其磁铁矿的颗粒明显较大.多畴磁铁矿的形成,可能和超高压变质岩折返过程中,花岗质片麻岩较强的流体活动相关.部分分布于花岗质片麻岩主体岩性段外的样品,具有较高的天然剩余磁化强度,则可能反映了花岗质片麻岩及周围榴辉岩之间的流体交换.
Through the detailed rock magnetism study and rock mineralogy analysis of the granitic gneiss in the main hole of the Chinese mainland scientific drilling project, the magnetic susceptibility of granitic gneiss (0.570 × 10-7 ~ 120.450 × 10-7 m3 · Kg-1 with an average of 29.996 × 10-7 m3 · kg-1) is second only to serpentine garnet peridotite in all the main pores of the rock, and its natural residual magnetization (0.002 × 10-3 ~ 2.109 × 10 -3 Am2 · kg-1 with an average of 0.210 × 10-3 Am2 · kg-1) is the lowest among all the lithologies.The magnetic susceptibility curves with temperature, alternating demagnetization curve and hysteresis loop show that granite The main composition of the magnetite assemblage in the gneisses is magnetite, and a small part of the sample contains hematite, in which the magnetite is dominated by multidomain, and the pseudo-monopolar magnetite only appears in a small amount of samples. Compared with amphibolite (totally degenerated eclogite) that is completely degenerated, the granitic gneisses have similar magnetic mineral assemblages, but their magnetite particles are obviously larger. The formation of multi-domain magnetite , Which may be related to the strong fluid activity of granitic gneiss during the reenforcement of ultrahigh-pressure metamorphic rocks, and some samples distributed outside the main lithology of granitic gneiss Natural high residual magnetization, it may reflect the fluid communication between the surrounding gneiss and eclogite.