黄土高原黄土－古土壤的矿物组成及其环境意义  

MINERAL COMPOSITION OF LOESS-PALEOSOL IN THE LOESS PLATEAU OF CHINA AND ITS ENVIRONMENTAL IMPLICATIONS

作　　者：郑洪汉[1] B．K．G．Theng J.S.Whitton 

机构地区：[1]中国科学院广州地质新技术研究所，广州510640 [2]DSIRLandResources,LowerHutt,NewZealand

出　　处：《地球化学》1994年第C00期113-123,共11页Geochimica

基　　金：中国科学院西安黄土与第四纪地质研究开放实验室资助

摘　　要：采自洛川和西峰剖面的３４个黄土－古土壤样品分为砂、粉砂、粘土三个粒级进行了矿物成分分析。结果表明，黄土高原黄土和古土壤的矿物组成基本一致，除了方解石和褐铁矿、磁铁矿因在样品处理时已被剔除未予计算外，其主要矿物是石英、云母、长石和绿泥石。这４种矿物占总量的８８％－９１％，其他矿物有高岭石、蒙脱石、蛭石和少量重矿物。不同地质剖面和不同地层层位的矿物差异主要表现为组成矿物在含量和粒度上的变化。洛川与西峰剖面、古土壤与黄土以及相同古土壤层的上部与下部相比，它们的矿物组成主要表现为前者含有较少长石和较多云母和蛭石，而且颗粒较细，表明在土壤发育过程中使矿物转变的生物化学风化过程和使矿物颗粒由粗变细的物理风化过程并存。这一结果有利于这样一种土壤发育机制解释，即古土壤发育与黄土堆积过程同时进行，只是在古土壤发育时期黄土的堆积过程缓慢，成土作用大于黄土堆积作用而发育土壤。A total of 34 loess-paleosol samples from the Luochuan and the Xifeng sections in the Loess Plateau, northern China, were separated into sand, silt and clay fractions,and their mineral compositions were analyzed.Analytical results indicate that the loess and the paleosol have similar mineral components.They consist of quartz, mica,feldspar and chlorite,which amount to 80 to 91 percent,and minor amounts of kandit,smectite,vermiculite and some heavy minerals.Calcite,limonite and magnetite are not analyzed because they have been removed in sample preparation.The difference of mineral compositions in samples from different sections and stratigraphic levels is mainly the variation of the amount and grain size of minerals.The Luochuan section,the paleosol and the upper part of the same paleosol layer contain less feldspar and more mica and vermiculite with respect to the Xifeng section,to the loess and to the lower part of the same paleosol layer,respectively,indicating the coexistence of biochemically weathering process,which caused the textural change of minerals,and the physically weathering process,which resulted in the changes of the grain size of minerals,during the soil-forming process.This favors the soil-forming mechanism that the loess deposition and the soil formation take place simultaneously,with the soil developing as a result of greater rate soil formation.

关 键 词：黄土高原 矿物组成 环境意义 黄土-古土壤 成矿机制 矿物变化 

分 类 号：P619.23[天文地球—矿床学] S153.61[天文地球—地质学]