PROGRESS IN GEOCHEMICAL RESEARCH ON THE LOESS AND OTHER QUATERNARY DEPOSITS IN CHINA
中国第四纪黄土地球化学研究进展

It is of great importance in correctly explaining their environmental significance of some climatic proxies to understand the evolution of minerals under the surficial condition. Rapid progresses have been made during past 30 years in China in the study of elemental geochemistry, stable isotopic and cosmic nuclide geochemistry, iron bearing minerals and biogeochemistry on loess and other Quaternary deposits. Elementary geochemical studies on loess made us to understand that desert and loess as a whole is a complex system. Chemical weathering took place both before the dust was blown in desert and after its accumulated in loess region. Any explanation of the results of chemical analysis of loess should take this into consideration. Stable isotope research on organic matter and carbonate in loess gives us bright future in paleoclimatic and paleoecological reconstruction but it is still a long way to know the processes of decomposition of original organic material and the mechanism of secondary carbonate in loess. Magnetic susceptibility variation of loess paleosol sequence is an important indicator of past environment changes. Our understanding of the behavior of iron bearing minerals during soil forming processes, i. e. the decrease of Fe 2+ content,subsequently increase of Fe 3+ content, in certain amount is the mineralogical basis for the magnetic enhancement of paleosol. Full oxidized of Fe 2+ will make susceptibility decrease for the most developed soils in the dust sequences in the Loess Plateau. Great attention should be paid to use the magnetic susceptibility as a proxy of the intensity of summer monsoon. Cosmic nuclides are newly developed technique for paleoclimatic study. The new data show that the effect of climatic change is dramatically expressed by 10 Be concentration. In the paleosols soil maturation processes are manifest in the 10 Be distribution within different size fractions, accompanied by downward movement to zones of high authigenic mineral concentration. In loess samples, at deposition, it had an appreciable endowment of 10 Be from dust source regions. These conclusions are useful for us to correctly use 10 Be as a tool to trace paleoenvironmental changes. Biogeochemical process in surficial environment is the field we know little about it. The study on the magnetic bacteria is an important probe in this field. It is still very far away from our fully understanding of real processes took place during the geological past, but we still think it is worth to introduce new development in this field to the readers. This is the year of 100th anniversary of the birth of the famous geologist and geochemist, late Professor Hou Defeng, who showed great concern to the geochemical study of Quaternary deposits and encouraged young scientists to explore in this field. We would like to offer this paper to his spirit. Had he heard the development in Quaternary geochemical studies, he would have smiled in his grave.$$$$