Effects of nanoscale exsolution in hematite-ilmenite on the acquisition of stable natural remanent magnetization
Effects of nanoscale exsolution in hematite-ilmenite on the acquisition of stable natural remanent magnetization
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DOI：
10.1016/j.epsl.2004.05.027
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发表时间：
2004-08-15
影响因子：
5.3
通讯作者：
Putnis, A
中科院分区：
文献类型：
--
作者：
Kasama, T;McEnroe, SA;Putnis, A
为了研究纽约州阿迪朗达克山脉罗素带岩石中高且稳定的天然剩磁（NRM）的获取机制，我们使用三个具有不同磁性的样品检查了磁性矿物的溶出微观结构和成分。样品含有具有钛铁矿片层的钛赤铁矿、无片层的端元赤铁矿和稀有磁铁矿作为NRM的潜在载体。钛赤铁矿的透射电子显微镜 (TEM) 观察和能量过滤 TEM (EFTEM) 的元素图表明，在数百纳米厚的较大钛铁矿片层之间存在丰富的最小厚度约为 2 nm 的非常细的钛铁矿片层。钛铁矿片层和钛赤铁矿基质的组成分别为Ilm(90-100)Hem(10-0)和Ilm(7-16)Hem(93-84)，共享(001)面，并且丰富的细钛铁矿片层与其钛赤铁矿基质具有连贯、尖锐的结构和成分界面。样品之间的比较表明，磁化强度与细外溶片层的数量相关。这些结果与片层磁性假说一致，表明高且稳定的NRM的获得与细钛铁矿片层与其宿主钛赤铁矿之间的界面面积有关。具有多畴磁性结构的端元赤铁矿仅对这些样品中的 NRM 贡献很小。 (C) 2004 Elsevier B.V. 保留所有权利。
To investigate the acquisition mechanism of high and stable natural remanent magnetization (NRM) in rocks of the Russell Belt, Adirondack Mountains, New York, we examined the exsolution microstructures and compositions of magnetic minerals using three samples with different magnetic properties. The samples contain titanohematite with ilmenite lamellae, end-member hematite without lamellae and rare magnetite as potential carriers for the NRM. Transmission electron microscopy (TEM) observations and element mapping by energy-filtered TEM (EFTEM) of the titanohematite indicated that very fine ilmenite lamellae with a minimum thickness similar to2 nm are abundant between larger ilmenite lamellae a few hundreds of nanometers thick. The ilmenite lamellae and titanohematite hosts, with the compositions of Ilm(90-100)Hem(10-0) and Ilm(7-16)Hem(93-84), respectively, share (001) planes, and the abundant fine ilmenite lamellae have coherent, sharp structural and compositional interfaces with their titanohematite hosts. Comparison between samples shows that the magnetization is correlated with the amount of fine exsolution lamellae. These results are consistent with the lamellar magnetism hypothesis, suggesting that the acquisition of high and stable NRM is related to the interfacial area between fine ilmenite lamellae and their host titanohematite. End-member hematite with a multi-domain magnetic structure only contributes a minor amount to the NRM in these samples. (C) 2004 Elsevier B.V. All rights reserved.