Observation of Nano/micro-scale Structures of Gouges in the Active Fault Zones
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摘要: 断层泥是研究活动断裂带运动性质和活动习性的重要介质。以往,对断层泥的研究主要借助偏光显微镜和低真空扫描电镜进行,观察到的现象有限。借助高真空扫描电镜从纳微米尺度对断层泥进行更精细化的研究,其方法是对野外断层泥进行定向原状样品采集,通过室内样品自然风干、微样制作、表面镀金和扫描电镜观察,从纳微米尺度研究a-b组构面和a-c组构面的各种变形现象。此方法可以帮助确定断层的运动性质、断层滑动面的新老关系,并可鉴别粘滑过程与蠕滑过程;同时,还可以对工程场地中发现的黏土滑动面进行鉴别,区分地震断层和非地震断层。Abstract: Gouges are the common product bydeformation in the shallow crust of the active fault zones. They are made up of unconsolidated clastic, rock grains and clay minerals. Generally, the width of gouges in a fault zone is only a few millimeters to tens of meters, while it formed from one earthquake motion which is just a few millimeters to several centimeters. Gouges record the history and retain all kinds of the active fault zones. Therefore, as an important medium, gouges are useful to study the movement and activity of the active fault zones. In this paper we use high vacuum scanning electron microscope to study of structures of gouges at nano/micro-scale. Firstly, original-state directional samples of gouges in the active fault zones are collected. Secondly, the samples are dried up naturally in laboratory before they are made into micro samples. Thirdly, before observing nano/micro-structures by high vacuum scanning electron microscope, the surfaces of micro samples need to be coated with a layer of gold. Lastly, all kinds of phenomena of deformations on fabric in a-b surface and fabric in a-c surface are analyzed. For example, striations, ridges, grooves, groups of striations in different directions, slickenside, steps and arrangement types of clay minerals can be observed from fabric in a-b surface. Folds, gravels surrounded by clay minerals, rotation, break, clastic particle packed by clay minerals and other phenomena of deformations can be observed from fabric in a-b surface. These phenomena represent different meanings and reflect different mechanical property, which is useful in study of the fault movement, fault age, faulting mode, and faulting type.
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Key words:
- Active fault zone /
- Gouges /
- Nano/micro-scale structure /
- Observation method
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图 1 黏土样品微纳、微米尺度对比观察
(a)自然沉积的黏土,水平方向,片状黏土矿物随机叠加(实箭头);(b)自然沉积的黏土,竖直方向,片状黏土矿物无规则排列;(c)取自钻孔的原状黏土,擦痕明显(实箭头);(d)图 1(c)方框区域局部放大,似“波动”状变形(虚线框区域)
Figure 1. Comparion of clay samples at the nano/micro-scale
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