金沙江巧家段冲积物动态图像法粒度特征研究  

Analysis on grain size of alluvial sediments in the Qiaojia segment, upper Yangtze River, based on dynamic image method

作　　者：王有鹏 李德文[1] 王锦鹏 WANG Youpeng;LI Dewen;WANG Jinpeng(Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration, Beijing, 100085)

机构地区：[1]中国地震局地壳动力学重点实验室/中国地震局地壳应力研究所,北京100085

出　　处：《地质论评》2019年第2期503-513,共11页Geological Review

基　　金：国家自然科学基金资助项目(编号:41471002)的成果~~

摘　　要：图像法作为国际地科联唯一推荐的粒度分析方法,长期受制于样本量不足的问题。基于新型快速成像和处理技术的动态图像法可在短时间内为样品建立海量颗粒的粒度粒形数据库,为天然沉积物粒度特征的直观表达开辟了广阔前景。本文以金沙江巧家段右岸支沟冲积扇沉积物为研究对象,对4个沉积剖面20个样品进行动态图像粒度分析,建立样品颗粒图像数据库,计算颗粒6种粒径,包括等效投影圆面积径(等积径),弗雷德(Feret)径三种(最大、最小和均值)以及最小外接矩形径两种(最大和最小)等,并与激光(衍射/散射)法测试结果进行对比。结果表明:①图像法所获6种粒径的中值粒径和均值粒径均较激光法粗,分选性较激光法优。②消除量程差异后的对比结果表明,激光法所测均值粒径仅为真实均值粒径(图像法结果)的3/10～1/2左右(差值为0.68～1.78φ);这种偏离可能与天然沉积物的多矿物属性和不规则性有关。③两种测试方法所获结果均能反映相同的剖面沉积物粒度相对变化趋势,在传统的沉积环境判别准则下均能反映基本一致的动力条件和堆积环境。这些认识为图像法粒度分析技术的应用和推广提供了技术支撑和解释依据。Image method, as the grainsize analysis method recommended only by the International Union of Geological Sciences, has long been constrained by insufficiency of sample capacity. The new dynamic image method, based on the new imaging and processing technology, can set up the database of mass grainsize in short time, and opens up broad prospects for direct expression of grainsize of natural sediment. In this study, the sediments of alluvial fan alone the bank of the Qiaojia segment, upper Yangtze River, are investigated. A total of 20 samples are collected from 4 profiles and are studied using methods of dynamic image and laser-diffraction. Based on dynamic image database of the samples, six type of grainsizes are calculated, including diameter of a circle of equal projection area, three kinds of Feret diameters(the max, min and mean), and two kinds of minimum external rectangular diameters(max and min). The results are also compared with those obtained by laser method. The study shows:① the median and mean grainsizes obtained by dynamic image method are coarser than those by laser method, and the sorting degree is better than that by laser method.② The comparison of the results normalized by same measurement range shows the mean diameter measured by laser method is only 3/10~1/2 of the true mean diameter(the result by dynamic image method)(the difference is 0.68~1.78 φ), this deviation may be related to the multimineral properties of natural sediments.③ The results obtained by the two methods can reflect similar trend of grainsize change in the profile, and can reflect the similar dynamic conditions and sedimentary environment under the traditional discrimination criteria of sedimentary environment. These knowledges provide technical support and explanation basis for the application and popularization of dynamic-image grainsize analysis.

关 键 词：支沟冲积扇 动态图像法 沉积环境判别 粒度分析 金沙江 

分 类 号：P512.2[天文地球—地质学]