阿尔泰山古风化壳的地球化学特征

在阿尔泰山零星残留着一系列古风化壳，本文主要运用土体化学组成分析，研究各类元素在不同母岩风化剖面上的迁移聚集趋势，并结合可溶盐，碳酸钙含量测定以及粘土矿物的Ｘ射线衍射分析，判断风化壳形成过程中淋溶作用的强弱，最终确定其风化程度。

THE GEOCHEMICAL CHARACTERISTICS OF THE PALEO-WEATHERING CRUSTS IN THE ALTAY MOUNTAINS

A number of small and isloated occurences of paleo-weathering crusts distribute over the Altay Mountains in China. By discribing these typical weathering profiles in terms of parent rocks and comparing their analytical data which include chemical analyses, mineral assemblage, X-ray diffraction identification of clay minerals and so on, the paper studies chemical elements mobility to estimate the degrees of development of paleo-weathering crusts. Based on the geochemical characterishcs, the paleo-weathering crusts can be classified into four kinds. The first on erepresents matured weathering profiles. They are usually covered with the Tertiary sediments. The profiles show an almost complete removal of alkaline and alkalineearth elements, relative release of silica and iron accumulation of alumininm and htanium. The second kind of weathering crusts represents a high degree of development. The most part of alkaline and alkaline-earth of development. The most part of alkaline and alkaline-earth elementsare removed out from the weathering profiles, silica is relatively released, aluminium and iron rather accumulated. The ratio SiO2/ Al2O3 is about 2.0. The third one is the most predominant kind. It generally indicates middle degree developed weathering profiles. On these profiles, differential concentration or residual elements resulted from their distinct geomorphological locations and lithological units. The fourth kind which developed on the Quaternary clastic only underwent a relatively weak weathering process. The ratio SiO2 / Al2O3 is from 5.6-7.9.These kinds of paleo-weathering crusts formed under differcnt paleo-climate and in differant periods. Under the present climate, the formation of these crusts can no longer develop, and the evolution leads them to dismember.