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天山黄土磁化率增强机制初步研究

期刊名称：宋友桂，NIE Jun-sheng，史正涛等，2010，地球环境学报，VOL.1(1):66-72
时间：0
分类：P318.4[天文地球—固体地球物理学;天文地球—地球物理学]
作者机构：[1]中国科学院地球环境研究所黄土与第四纪地质国家重点实验室,西安710075, [2]Jackson School of Geosciences, University of Texas at Austin, Austin TX 78712,USA, [3]云南师范大学地理与旅游学院,昆明650092
相关基金：Nature Science Foundation of China （40972230, 40772116, 40871018） ; National Basic Research Program of China （2010CB833406） ; Chinese polar scientific strategic studies fund of State Oceanic Administration （20070226）
相关项目：伊犁盆地不同海拔晚更新世黄土剖面磁化率特征相反原因研究

关键词：磁化率, ARM, 天山黄土, 中亚, 黄土高原, magnetic susceptibility , ARM , Tianshan loess , Central Asia , Loess Plateau

中文摘要：

过去20多年，中外学者对黄土高原黄土磁化率增强机制进行了系统研究，取得了重要进展，但对中国黄土高原之外黄土磁化率增强机制研究仍十分薄弱。作者对地处中亚的天山北麓的一个7m厚的黄土剖面进行了初步的磁学研究。结果表明，该剖面黄土质量磁化率Xlf与频率磁化率Xfd呈较好的线性关系，说明该剖面的磁化率增强机制与黄土高原黄土类似，磁化率增强主要受控于超细和多畴磁性颗粒的含量，可以用磁化率成壤模式解释。然而，质量磁化率Xlf与非磁滞磁化率XARM相关关系较弱，表明稳定单畴磁铁矿／磁赤铁矿对磁化率增加的贡献是有限的，多畴颗粒对磁化率的贡献较大，说明与黄土高原磁化率增强机制在细节还是有所差别。同时，发现天山黄土磁化率的初始值（Xlf0）（当表征成壤程度的频率磁化率差值（Xfd）为零时）差不多是黄土高原的2倍，说明天山黄土与黄土高原黄土来源不同。

英文摘要：

Magnetic enhancement mechanisms of the Chinese Loess Plateau （CLP） loess samples have been well studied. In contrast, magnetic enhancement mechanisms for loess samples from outside the CLP have not been fully understood. Here we present a preliminary magnetic study of an about 7 m loess section located at the northern slope of the Tianshan Mountain, Central Asia. We found that, similar to the CLP loess, Xlf （ magnetic susceptibility measured at 470 Hz ） of the Tianshan loess is linearly correlated with Xfd（ Xlf - Xhf）（ Xhf, measured at 4700 Hz）, indicating that enhancement of magnetic susceptibility of the Tianshan loess is in general controlled by concentration of ultrafine ferrimagnetic grains. The strong correlation between Xfd and Xlf indicates that magnetic enhancement of the Tianshan loess can be explained by pedogenic model. However, different from the CLP loess, the correlations between Xlf and XARM is weak, indicating that enhancement of magnetic susceptibility for the Tianshan loess is not determined by concentration of stable single domain magnetite/maghemite. We also found that Xlf0 （ Xlf value when Xfd=O） for the Tianshan loess is roughly twice that for the CLP loess, indicating that dust source for the Tianshan loess is different from that for the CLP loess.

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