刘雁江^1,,
刘彩彩^1,,,
张竹琪¹,
刘康¹,
任治坤²,
张会平¹,
李传友²,
徐红艳¹,
李雪梅¹
1. 中国地震局地质研究所 地震动力学国家重点实验室, 北京 100029
2. 中国地震局地质研究所 活动构造与火山实验室, 北京 100029

基金项目: 国家重点研发计划重点专项课题（2017YFC1500104），青藏高原第二次科学考察项目（2019QZKK0704），国家自然科学基金项目（41622204，41761144071，41474053，41661134011），国家重点实验室自主课题（LED2014A03）联合资助


详细信息

作者简介: 刘雁江, 男, 1992年生, 硕士研究生, 2015年毕业于合肥工业大学, 主要从事断层磁学与活动构造研究.E-mail:1834297618@qq.com

通讯作者: 刘彩彩, 女, 1984年生, 博士, 副研究员, 2010年毕业于中国科学院地质与地球物理研究所, 主要从事古地磁学与构造地质学研究.E-mail:liucaicai@126.com

中图分类号: P318

收稿日期:2019-03-22
修回日期:2019-07-28
上线日期:2020-06-05

Rock magnetic studies of fault rocks from the Laohushan segment of the Haiyuan fault zone and its tectonic implications

LIU YanJiang^1,,
LIU CaiCai^1,,,
ZHANG ZhuQi¹,
LIU Kang¹,
REN ZhiKun²,
ZHANG HuiPing¹,
LI ChuanYou²,
XU HongYan¹,
LI XueMei¹
1. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
2. Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China


More Information

Corresponding author: LIU CaiCai,E-mail:liucaicai@126.com

MSC: P318

--> Received Date: 22 March 2019
Revised Date: 28 July 2019
Available Online: 05 June 2020


摘要
摘要:断层岩，尤其是断层泥的磁性异常近年来被研究人员广泛关注，但关于其磁性异常的形成原因尚没有统一的解释.海原断裂是青藏高原东北缘一条重要的走滑断裂，前期研究发现海原断裂带景泰段出露有数十米至上百米的断层岩，是理想的研究材料.本研究选取海原断裂带景泰段老虎山山前一个断层岩剖面作为研究对象，拟通过测量断层岩的磁化率（χ）、非磁滞剩磁（ARM）、饱和等温剩磁（SIRM）、等温剩磁（IRM）以及磁化率随温度变化曲线（χ-T曲线）等磁学参数并结合粒度、碳含量、X射线衍射（XRD）等分析方法来探究海原断裂带老虎山段不同颜色断层岩的磁性特征及其形成机制.磁学研究显示黑色、红色及杂色断层泥相较于围岩和破碎带显示了低磁性，尤其是黑色断层泥，其磁化率值均小于10×10^-8m³·kg^-1.碳含量及矿物相分析结果指示黑色断层泥与断裂带附近石炭系煤层具有相似的矿物相组成，结合相似的χ-T曲线推断石炭系煤层为黑色断层泥的母岩.石炭系煤层经断层活动卷入断层，在断层强烈剪切摩擦作用下不断细化，形成伊利石等黏土矿物，并促使一部分顺磁性含铁硅酸盐矿物或其他含铁矿物发生化学变化形成亚铁磁性矿物，使得黑色断层泥的磁化率较其母岩石炭系煤层有一定升高.通过黑色断层泥的铁磁性磁化率结合χ-T曲线计算获得断层泥所经历的最高温度约为420℃，不超过450℃.老虎山段厚层碳质断层泥的存在为该地区发现的浅层蠕滑现象提供了一种解释.
关键词: 海原断裂带/
老虎山断裂/
断层泥/
磁化率/
χ-T曲线

Abstract:Fault rocks, especially fault gouge, have recently attracted more and more interests of researchers, but formation mechanism of its magnetic abnormality has not been decided yet. Outcrops of fault rocks with a thickness of several meters to a dozens of meters, has been found on the Jingtai segment of Haiyuan Fault. These fault rocks are good research materials. A fault rock profile in Laohushan mountain of the Jingtai segment has been investigated in this study. Magnetic susceptibility (χ), anhysteresis remanent magnetization (ARM), saturation isothermal remanent magnetization (SIRM), isothermal remanent magnetization (IRM) and magnetic susceptibility versus temperature curve (χ-T curve) and other magnetic parameters combined with particle size, carbon content and XRD analyses have conducted on the fault rocks to explore the formation mechanism and tectonic implication of different colored fault rocks in the Laohushan section of the Haiyuan fault zone. Rock magnetic results show that red, black, and variegated fault gouge show low magnetic susceptibility compared with the surrounding rock and fracture zone, especially the black fault gouge with a mean magnetic susceptibility of less than 10×10^-8 m³·kg^-1. The thermalmagnetic results combined with carbon content and mineral phase analyses indicate that the black fault gouge has a similar mineral composition to the Carboniferous coal near the fault zone. It is inferred that the Carboniferous coal is the parent rock of the black fault gouge. The Carboniferous coal was involved into the fault zone by active fault, and was continuously grinded under the strong shearing and friction of the fault, forming clay minerals such as illite and promoting the chemical transformation of a part of the paramagnetic iron-containing silicate mineral or other iron-containing minerals. This makes the magnetic susceptibility higher in the black fault gouge compared with the diamagnetism of their parent rock, the carbon layer. The maximum temperature is about 420 ℃, absolutely no more than 450 ℃, when the black fault gouge was formed, calculated from comparing the ferri-χ of the gouge with the χ-T curve of the coal. The presence of this high-carbon and thick fault gouge may be related to the shallow creep phenomenon on this fault.
Key words:Haiyuan fault zone/
Laohushan Fault/
Fault gouge/
Susceptibility/
χ-T curves



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