摘要
富碱斑岩带分布较广,目前对其风化过程中的元素地球化学行为研究较少。笔者等以滇中姚安富碱斑岩为例,通过对其化学风化过程的研究,有助于了解富碱斑岩成土过程中元素富集贫化控制因素,丰富碱性岩浆岩风化成土理论。笔者等分析了富碱斑岩风化过程中的矿物风化特征、元素含量分布特征、化学风化趋势、元素迁移富集特征及主控因素,结果表明:富碱斑岩各风化层元素含量与基岩具有继承性,体现了原位风化的特征,符合北亚热带季风气候下云南境内上扬子地块岩石的风化特征;与大陆上地壳组成(UCC)相比,风化成土过程中Ca、Na、K等阳离子强烈淋失亏损,Fe、Al富集;化学风化过程主要发生脱Ca、Na、K、Mg、Si与富Al、Fe作用,风化早期主要为去Ca、去Na过程,风化中、晚期为去K、去Mg、富Al、富Fe过程,并伴随着强烈的脱硅作用;结合迁移系数,常量元素活动性强弱顺序为:Ca>Na>K>Mg>Si>Al>Fe;微量元素地球化学行为一方面主要受地球化学性质相似的常量元素行为控制,另一方面受Al、Fe氧化物/氢氧化物和黏土矿物吸附作用的影响,Sm、Nb、Sc、Th、Ti、U、Y、Cu、Cr、Ni随风化原地残余富集,Ba、Rb、Sr与K、Na、Ca、Mg等常量元素行为一致,随风化而淋失迁出。
Alkali-rich porphyry zones are widely distributed,but the geochemical behavior of elements in weathering process is rarely studied.Taking Yao’an alkali-rich porphyry in central Yunnan as an example,the study on its chemical weathering process is helpful to understand the controlling factors of element enrichment and dilution in the process of alkali rich porphyry soil-forming and enrich the theory of alkaline magmatic rock weathering soil-forming.Methods:The characteristics of mineral weathering,distribution characteristics of element content,trend of chemical weathering,migration and enrichment characteristics of elements and main controlling factors of alkali-rich porphyry weathering were analyzed.Results:The content of elements in the alkaline-rich porphyry regolith is inherited from the bedrock,which reflects the characteristics of in-situ weathering,and accords with the weathering characteristics of the rocks in the Upper Yangtze block of Yunnan under the North subtropical monsoon climate.Compared with continental upper crust composition(UCC),Ca,Na,K and other cations are strongly eluted and depleted,while Fe and Al are enriched.The chemical weathering process is mainly characterized by decarbonization of Ca,Na,K,Mg,Si and enrichment of Al and Fe.Ca and Na are mainly involved in the early stage of weathering.In the middle and late stages of weathering,the processes are mainly K and Mg removal and Al and Fe enrichment,accompanied by strong desilication.Conclusions:The order of activity of major elements was Ca>Na>K>Mg>Si>Al>Fe;On the one hand,the geochemical behavior of trace elements is mainly controlled by the behavior of major elements with similar geochemical properties.On the other hand,the trace elements are affected by Al,Fe oxides/hydroxides and adsorption of clay minerals.Sm,Nb,Sc,Th,Ti,U,Y,Cu,Cr and Ni are enriched in situ with weathering.The geochemical behavior of Ba,Rb,Sr is consistent with K,Na,Ca,Mg and other major elements,and leaching out with weathering.
作者
徐磊
赵萌生
程琰勋
潘江涛
管继云
张亚
徐杰
陈伟志
王浩宇
黄加忠
杨明龙
巴永
王守营
XU Lei;ZHAO Mengsheng;CHENG Yanxun;PAN Jiangtao;GUAN Jiyun;ZHANG Ya;XU Jie;CHEN Weizhi;WANG Haoyu;HUANG Jiazhong;YANG Minglong;BA Yong;WANG Shouying(Kunming Natural Resources Comprehensive Research Center,China Geological Survey,Kunming650100;Technology Innovation Center for Natural Ecosystem Carbon Sink,Ministry of Natural Resources,Kunming650100)
出处
《地质论评》
CAS
CSCD
北大核心
2024年第2期512-528,共17页
Geological Review
基金
中国地质调查局地质调查项目(编号:ZD20220211,ZD20220210)的成果。
关键词
富碱斑岩
化学风化
常量元素
成土过程
地球化学行为
主控因素
姚安
alkali-rich porphyry
chemical weathering
major element
soil-formation process
geochemical behavior
main controlling factor
Yao’an
