The implications of the magnetism of ordinary chondrite meteorites
The implications of the magnetism of ordinary chondrite meteorites
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普通球粒陨石磁性的意义
DOI：
10.1016/0012-821x(92)90083-8
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发表时间：
1992
影响因子：
5.3
通讯作者：
D. Collinson
中科院分区：
文献类型：
--
作者：
S. Morden;D. Collinson
本文分析了11种普通铁磁材料（8种LL铁磁材料和3种L铁磁材料）的磁性。将样品重复破碎并定向到共同的参考方向，在每个阶段测量自然反射磁化强度（NRM）、磁化率（χ）和磁化率的各向异性。研究了某些碎片对交变场（a.f.）退磁、热退磁、等温剩磁（剩磁）和磁滞已被测量。结果发现，稳定的NRM的取向是随机的，下至0.1 mm 3的尺度。4-6型中的主要磁性载体是有序的铁镍矿物γ″-四镍铅矿。所测得的3型不含四纹石，NRM由细粒纹石携带。磁织物，类似于物理织物，被发现在所有的样品。除了两个，其他的都是片状的。塔克图克和沃尔德小屋显示线理。NRM的热退磁显示出更高的阻塞温度的趋势，为类型3-5的类型6磁铁矿。由于大多数样品的组构是连续的，而NRM随机取向，因此得出结论，磁性载体在陨石中就位之前被磁化，并且陨石不是细尺度角砾岩。随机NRM的保存导致热吸积的偏好作为产生变质织构的机制，而不是变质再加热，因为这将倾向于消除随机磁化。
The magnetic properties of eleven ordinary chondrites (eight LL-chondrites and three L-chondrites) have been analysed. The samples were repeatedly fragmented and oriented to a common reference direction, natural remanent magnetisation (NRM), susceptibility (χ), and anisotropy of susceptibility measured at each stage. The response of some fragments to alternating field (a.f.) demagnetisation, thermal demagnetisation, isothermal remanent magnetisation (IRM), and magnetic hysteresis has been measured. It was found that the orientation of the stable NRM was random, down to a scale of ∼ 1 mm3. The dominant magnetic carrier in types 4–6 was the ordered iron-nickel mineral γ″-tetrataenite. The type 3's measured contained no tetrataenite and the NRM was carried by fine-grained taenite. A magnetic fabric, analogous to a physical fabric, was found in all samples. In all but two, the fabric was foliated. Tuxtuac and Wold Cottage showed lineation. Thermal demagnetisations of NRM showed a trend towards higher blocking temperatures for type 6 chondrites over types 3–5. Because the fabric was continuous in the majority of samples, and the NRM randomly orientated, it was concluded that the magnetic carriers were magnetised before emplacement in the meteorite, and that the meteorites are not finescale breccias. The preservation of the random NRM leads to the preference of hot accretion as the mechanism for producing chondritic textures, as opposed to metamorphic reheating, as this would tend to erase the random magnetisation.