An Investigation of the Origin of Stable Remanence in Magnetite-bearing Igneous Rocks
An Investigation of the Origin of Stable Remanence in Magnetite-bearing Igneous Rocks
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含磁铁矿火成岩中稳定剩磁的成因研究
DOI：
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发表时间：
1969
期刊：
影响因子：
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通讯作者：
M. McElhinny
中科院分区：
文献类型：
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作者：
M. Evans;M. Evans;M. McElhinny
已经进行了旨在阐明火成岩中高稳定性剩磁的性质和来源的实验。使用的样品（来自南非的莫迪佩辉长岩）中的许多辉石颗粒含有小型（从几微米到光学极限）磁铁矿包裹体，其中一些由于其尺寸和形状而很可能是单域的。结果表明，这些夹杂物对 TRM 贡献很大，并且实际上可能解释了几乎所有的剩磁。测得的矫顽力高达 1800 – 归因于观察到的一些磁铁矿夹杂物的形状各向异性。对各种矫顽力理论的讨论表明，这是使磁铁矿具有超过1000奥斯特矫顽力的唯一机制。所得出的结论只能严格应用于这种特定的岩石；然而，人们认为单畴磁铁矿的自然存在比以前想象的更为常见。类似观测结果相对罕见的原因很可能是解释火成岩中典型TRM所需的磁铁矿的微小尺寸和非常小的总量。
Experiments designed to elucidate the nature and source of high-stability remanence in igneous rocks have been carried out. Many of the pyroxene grains of the samples used (from the Modipe gabbro of southern Africa) contain small (from a few microns down to the optical limit) magnetite inclusions, some of which are very probably single-domained by virtue of their size and shape. It is shown that these inclusions contribute significantly to the TRM, and may, in fact, account for virtually all of the remanence. Measured coercivities as high as 1800 œ are attributed to the observed shape anisotropy of some of the magnetite inclusions. A discussion of the various theories of coercive force indicates that this is the only mechanism which enables magnetite to possess coercivities in excess of 1000 oersteds.The conclusions reached can be strictly applied only to this particular rock; however, it is felt that the natural occurrence of single-domained magnetite is more common than previously supposed. The reason for the comparative rarity of similar observations may well be the minute size and very small total quantity of magnetite necessary to account for typical TRM's in igneous rocks.