摘要
黑云母是相对容易化学风化的常见矿物,可作为地表岩石风化程度的指示剂。为了研究黑云母在化学风化过程中的物理性质和化学成分的变化,本文对采自烟台院格庄花岗岩体风化壳中的黑云母进行了系统分析。样品经过分选、密度测量、化学测试和XRD衍射分析,结果表明,黑云母随着风化程度的增强,其颜色从黑色渐变为褐色乃至红褐色,硬度变小,挠性增强,密度由3.00 g/cm^(3)以上逐步减小至2.45 g/cm^(3)以下。矿物结构面网间距变大,结构和主要成分变化引发矿物相转变,矿物种类由黑云母→云母型混层矿物→水黑云母-蛭石混层矿物→蛭石;随着风化程度的增强,黑云母中SiO_(2)、Al_(2)O_(3)和Na_(2)O的含量逐渐增多富集,而TFeO、MgO、MnO、TiO_(2)、K_(2)O、CaO和P_(2)O_(5)含量减少流失,流失强度依次为K>P>Mn>Mg>Ti>Fe>Ca,K流失最大可达90%以上,其它元素也有30%~60%的流失率,风化黑云母密度变得越小其主要元素的迁移/富集率越大。风化壳全岩CIA指数小于70,风化云母的CIA介于57~85之间,院格庄花岗岩风化壳尚处于中等风化阶段。
Biotite is a common mineral,that is relatively easy to be chemically weathered,and can be used as an indicator for the degree of weathering of surface rocks.In order to study the changes of its physical properties and chemical compositions during the process of chemical weathering,in this paper,we have systematically analyzed the biotite in the weathering crust of the Yuangezhuang granite pluton in the Yantai area.The samples were sorted,density measured,chemical tested and XRD diffraction analyzed.The results show that with the increase of weathering degree of biotite,its color is gradually changed from black to brown and even to reddish brown,its hardness is decreased,its flexibility is increased,its density is gradually decreased from above 3.00g/cm^(3) to below 2.45g/cm^(3),its crystal plane spacing is increased,the changes of its structure and main components triggered the transformation of its mineral types from biotite to mica mixed layer mineral to hydrobiotit-vermiculite mixed layer mineral to vermiculite.In addition,with the increase of weathering degree,the contents of SiO_(2),Al_(2)O_(3) and Na_(2)O in weathered biotites are gradually increased,while their contents of TFeO,MgO,MnO,TiO_(2),K_(2)O,CaO and P_(2)O_(5) are decreased following the subsequent order of K>P>Mn>Mg>Ti>Fe>Ca,at the maximum loss rate of over 90% for K,and loss rates of 30-60% for other major elements.The smaller of densities of weathered biotites,the greater of migration/enrichment rates of their major elements.The CIA indexes of bulk rocks in the weathered crust are less than 70,while CIA values of the weathered biotites range from 57 to85.The weathering crust of the Yuangezhuang granite pluton was formed in the middle-class weathering stage.
作者
党丽丽
金秉福
樊水淼
张伟
施南
DANG Li-li;JIN Bing-fu;FAN Shui-miao;ZHANG Wei;SHI Nan(School of Resources and Environmental Engineering,Ludong University,Yantai 264025,China;Qingdao Engineering Consulting Institute(Ludong Branch),Qingdao 264299,China;School of Earth Science and Resources,China University of Geosciences,Beijing 100083,China)
出处
《矿物学报》
CAS
CSCD
北大核心
2022年第3期397-412,共16页
Acta Mineralogica Sinica
基金
国家自然科学基金项目(编号:41576057)。
关键词
黑云母
风化壳
黑云母密度
常量元素
院格庄花岗岩体
biotite
weathering crust
biotite density
major elements
Yuangezhuang granite pluton
