干旱区生态环境知识资源中心(Arid): 黄土中的碳酸盐矿物特征与化学风化

Arid

	黄土中的碳酸盐矿物特征与化学风化
其他题名	CHARACTERISTICS OF CARBONATE MINERALS IN LOESS AND ITS IMPLICATION FOR CHEMICAL WEATHERING
	梁莲姬 1; 孙有斌 2; 宋友桂 2
来源期刊	第四纪研究
ISSN	1001-7410
出版年	2014
卷号	34 期号:3 页码:645-653
中文摘要	从中国黄土沉积中提取古环境演化信息已取得重大进展,然而,如何有效区分黄土中原生和次生碳酸盐,进而用于追踪粉尘的来源和揭示风化成壤的强度,仍有很大困难。为了辨别黄土中不同成因的碳酸盐矿物,本文从黄土高原西部靖远和古浪剖面中选取2个典型古土壤和黄土样品(S_0和L_1),分为5个粒级(<4mum,4~8dmum,8-16mum,16-32mum和32~63mum),进行了热重分析(TGA)和X射线衍射测试(XRD)。结果表明:1)黄土中的碳酸盐主要由方解石和白云石组成,原生方解石和白云石在黄土中的含量比古土壤中含量高,并偏富集于粗颗粒组分;2)次生方解石在古土壤中的含量比黄土中高,并显著富集于细颗粒组分。在黄土和古土壤全样和分粒级样品中,TGA和XRD方法分别测出的Carb-B/Carb-A和(方解石+白云石)/方解石比值变化一致,有望成为反映黄土风化成壤强度的新代用指标。
英文摘要	Carbonate minerals in Chinese loess have been studied intensively to infer changes in chemical weathering and pedogenic intensity. However, effective discrimination of the primary and secondary carbonates remains difficult, which hampers greatly the application of primary dolomite and secondary calcite as a sensitive provenance and paleoclimatic tracer, respectively. In this paper, we selected the two representative eolian samples from S_0 and L_1 layers of the Jingyuan (36. 35°N, 104.6°E; 2210m above sea level) and Gulang (37°49’N, 102°88’E; 2400m above sea level) loess sequences, which are located in the northwestern Chinese Loess Plateau. Due to their proximity to Tengger desert, loess sequences in these regions are characterized by high sedimentation rates and permit robust evaluation of rapid monsoon changes. We separated all bulk samples into five size fractions (<4mum, 4 ~ 8mum, 8 ~ 16mum, 16 ~ 32mum and 32?63mum) using pipette (<4mum, 4?8mum,8 ~ 16mum and 16 ~ 32mum size fractions) and wet-sieving methods (32 ~ 63mum size fraction),respectively. Four bulk and twenty size-separated samples were conducted for the Thermo gravimetric analysis (TGA) and X-ray diffraction (XRD) to identify the types and concentrations of different carbonate minerals. The TGA results show (1) Carb-A (thermally decomposed between 615?840°C) exhibits higher content in paleosoil than in loess and is dominantly enriched in fine fractions, indicating that this type of carbonate mineral is mainly related with the exsitence of secondary carbonates, (2) Carb-B (thermally decomposed between 840 ?1000°C) is higher in loess than paleosoil and enriched mainly in the coarse fractions, which is closely associated with the concentration of primary calcite and dolomite. The XRD results show Calcite/Quartz ratio is higher in fine fractions, while Dolomite/Quartz ratio exhibit unapparent trends in different size fractions. Our study indicates that the variation of Carb-B/Carb-A ratio mainly reflects the relative concentrations of primary and secondary carbonate minerals, consistent with (Calcite + Dolomite) /Calcite ratio by XRD in the loess-paleosol bulk and size samples. Compared with the XRD-derived (Calcite+Dolomite) /Calcite ratio, the Carb-B/Carb-A ratio is more likely to be a new sensitive indicator of the chemical weathering intensity, permitting a robust investigation of rapid summer monsoon changes in the weakly weathered loess sequences in the northwestern Chinese Loess Plateau.
中文关键词	黄土 ; 碳酸盐 ; 方解石 ; 白云石
英文关键词	TGA XRD loess carbonate calcite dolomite TGA XRD
语种	中文
国家	中国
收录类别	CSCD
WOS类目	GEOLOGY
WOS研究方向	Geology
CSCD记录号	CSCD:5143891
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/231005
作者单位	1.中国地震局地质研究所, 地震动力学国家重点实验室;黄土与第四纪地质国家重点实验室, 北京 100029, 中国; 2.中国科学院地球环境研究所, 黄土与第四纪地质国家重点实验室, 西安, 陕西 710075, 中国
推荐引用方式 GB/T 7714	梁莲姬,孙有斌,宋友桂. 黄土中的碳酸盐矿物特征与化学风化[J],2014,34(3):645-653.
APA	梁莲姬,孙有斌,&宋友桂.(2014).黄土中的碳酸盐矿物特征与化学风化.第四纪研究,34(3),645-653.
MLA	梁莲姬,et al."黄土中的碳酸盐矿物特征与化学风化".第四纪研究 34.3(2014):645-653.