云南省西部地区土壤地球化学基准值特征及成因分析

Characteristics and Genesis of Soil Geochemical Baselines in Western Yunnan Province

基于云南省西部地区土地质量地球化学调查数据资料,采用具有稳健特性的中位数表征深层土壤52种元素的地球化学基准值,对比分析了不同成土母质和用地类型的元素分布特征和富集贫化规律,进一步采用因子分析从元素组合特征角度剖析了地球化学基准值的成因机制。结果表明:研究区土壤中铁族元素、亲铜元素、矿化剂和卤族元素、稀有稀散稀土元素、放射性元素、钨钼族元素、造岩元素等多数元素基准值偏高;碱土金属等元素基准值明显偏低,其中CaO和Na_(2)O基准值仅为全国水平的13%和7%;成土母质是土壤元素基准值的主要控制因素,用地类型对基准值有一定的影响;区内土壤中铁族元素TFe_(2)O_(3)、V、Co、Cr高基准值主要受基性成土母岩的控制,W、Sn、Pb主要与中高温岩浆成矿作用有关,生命元素C、N、S、P、Se与土地利用类型及其表生地球化学作用有关;母岩母质类型及风化淋滤作用、矿化作用、生物富集作用、黏土物理化学吸附作用,共同影响着土壤基准值特征,其中母岩的风化作用有重要影响。研究成果为区域资源环境评价提供了基础地球化学信息。

Based on the geochemical survey data of land quality in western Yunnan Province,the median with robust characteristics was used to represent the geochemical baselines of 52 elements in deep soil.The distribution and enrichment and dilution features of elements in different parent materials and land use types were compared and analyzed.The causes of geochemical baselines were further analyzed from the perspective of element combination characteristics by factor analysis mechanism.The results showed that the baselines of iron group elements,chalcophile elements,mineralizer and halogen elements,rare,scattered,rare earth metal elements,radioactive elements,tungsten molybdenum group elements and rock-forming elements in the study area were higher than those of national geochemical baselines;the baseline values of alkaline earth metals were significantly lower,of which CaO and Na_(2)O only with 13%and 7%of the national level;soil parent material was the main control factor of soil element baseline values.The high baselines of TFe_(2)O_(3),V,Co and Cr were mainly controlled by basic parent rocks,W,Sn and Pb were mainly related to the high temperature magmatic mineralization,the life elements including C,N,S,P and Se were related to land use types and supergene geochemical cycle.The results showed that the types of parent rock,weathering leaching,mineralization,bioaccumulation and physicochemical adsorption of clay jointly affect the characteristics of soil baselines,among which the weathering of parent rocks had an important influence.The results provide foundational geochemical information for regional resource and environment assessment.