Mineral Composition and Their Weathering Significance of Zhaosu Loess——Paleosol Sequence in the Ili Basin, Xinjiang
详细信息
- 责任者：Zeng Mengxiu (State Key Laboratory of Loess and Quaternary Geology ; Institute of Earth Environment ; Chinese Academy of Sciences ; Xi’an 710075 ; China) ; Song Yougui
- 刊名：Geological Review
- 出版年：2013
- 卷期：59(3)
- 关键词：黄土 ; loess ; 伊犁盆地 ; Yili Basin
- 页码：p.575-586
- 图表：illus., 1 table, 48 refs.
- 分类号：1400
- issnNo：ISSN0371-5736
- isbnNo：CN11-1952/P
摘要
The loess record in the Ili basin dominated by westerly provides an important archive of regional climate and environmental change. However,in contrast to the widely investigated loess deposits in Chinese Loess Plateau,Ili loess – paleosol sequences are still insufficiently known and poorly understood. During the past decade,the lithology,genesis,sources,geochemical composition and distribution of the Ili loess as well as the paleoclimatic significance of various proxies such as magnetic susceptibility have been investigated. However,there are few reports about mineralogy and weathering history of Ili loess. Based on X-ray diffraction analysis,the authors carried out the mineral composition and particle size distribution of both 138 bulk samples and 45 different grain size fractions from Zhaosu loess—paleosol section in the Ili basin,Xinjiang. Levenberg—Marquardt ( LM) method was applied to compute the content of 8 kinds of minerals with mixed standard material quantitative Corundum. The results showed that the calculated values of corundum were in good agreement with given ratio values,the loess was mainly consisted of quartz,calcite,chlorite,plagioclase,hornblende,K-feldspar,dolomite and muscovite. The distribution of calcite was uniform within each grain size fractions,the coarse sediment were dominated by quartz, plagioclase,dolomite,hornblende and K-feldspar,the chlorite in <16μm size fraction achieve a considerably higher content than other minerals,the muscovite in 16～32 ’m size fraction had low content and in other size fractions had higher content. The minerals content and their ratios can show the variety of environment and the intensity of weathering in Ili loess. Those mineralogy indicators showed that the Zhaosu loess—paleosol sequence had weak chemical weathering,but the intensity of chemical weathering of paleosol were stronger than loess layers. The intensity of physical weathering in Zhaosu section during the past 80000 years can be reconstructed as strong physical weathering at S1 ,weaker physical weathering at L1L2 and L1S1 ,stronger physical weathering at L1L1 ,then the physical weathering intensity became increased and decreased gradually at the stage of S0 .
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