干旱区生态环境知识资源中心(Arid): 宜昌三斗坪地区南华系化学蚀变指数特征及南华系划分、对比的讨论

Arid

	宜昌三斗坪地区南华系化学蚀变指数特征及南华系划分、对比的讨论
其他题名	The Character of the Chemical Index of Alteration and Discussion of Subdivision and Correlation of the Nanhua System in Yichang Area
	王自强 1; 尹崇玉 2; 高林志 2; 唐烽 2; 柳永清 2; 刘鹏举 2
ISSN	0371-5736
出版年	2006
卷号	52 期号:5 页码:577-585
中文摘要	化学蚀变指数(chemical index of alteration)最早作为判别源岩区化学风化程度的指标而提出，随后又应用于对沉积物沉积环境的判定。化学蚀变指数的表达式为CIA＝n(Al_2O_3)／[n(Al_2O_3)＋n(CaO~)＋n(Na_2O)＋n(K_2O)]100。CaO~代表硅酸盐中的CaO，n(CaO~)＝n(CaO)－n(CO_2，方解石)－0.5·n(CO_2，白云石)－10／3·n(P_2O_5)。化学蚀变指数研究样品的选取极为重要，最佳岩性为细碎屑岩，需要清除成岩过程中钾交代作用的影响。用成分变异指数(ICV)来判别沉积再循环作用和沉积物成分被改造的程度。用A-CN-K三角图解来判别物源区的源岩性质和样品钾交代的特征及其风化趋势。宜昌三斗坪地区南华系CIA研究表明：该区南华系下统莲沱组下部的CIA值在50～65之间(干燥寒冷)，上部为65～75之间(温暖潮湿)和顶部为55～60之间(干燥寒冷)；南华系上统南沱组的CIA值基本在60～65之间(干燥寒冷)，近顶部两个样品的CIA值达70(温暖潮湿)。上述CIA值变化表明本区南华纪经历自老到新由冰期干燥寒冷-间冰期温暖潮湿-冰期干燥寒冷沉积环境的变化过程。本文据此提出了新的扬子古陆南华系新的划分和对比方案。
英文摘要	The chemical index of alteration(CIA)is first proposed as a marker to distinguish the chemical weathering degree of source rocks, and later it is used to distinguish the depositional environment of sediments. The formula of the chemical index of alteration is CIA＝n(Al_2O_3)／[n(Al_2O_3)＋n(CaO~)＋n(Na_2O)＋n(K_2O)]100, here, CaO~* represents CaO in silicates, n(CaO~*)＝n(CaO)－n(CO_2，calcite)－0.5·n(CO_2，dolomite)－10／3·n(P_2O_5). It is very important to select samples for analyses of the chemical index of alteration. Following two factors have to be considered when sampling in the field. First, the best rocks are the fine clastic rocks. Second, the influence of diagenetic potassium replacement should be avoided. The index of compositional variability (ICV)is used to distinguish circulation and reformed degree of the composition of sediments. At the same time, A-CN-K diagram is used to distinguish the feature of source rock and character of potassium replacement and its weathering degree. Our results show that the value of CIA is at 5O~65 in the lower part, 65～75 in the upper part and 55～60 in the top part of the Liantuo Formation, Lower series of Nanhua. The value of CIA varies between 60～65 in the Nantuo Formation, but is up to 70 at the top of the Nantuo Formation at Sandouping, Yichang area. Variation of the value of CIA indicates separately the circle of the arid-frigid low chemical weathering environment to warm damp medium chemical weathering environment and to arid-frigid low chemical weathering environment from base to the top in the section. The results demonstrates that the lower part of the Liantuo Formation represents an arid-frigid cold ice period, the upper part of the Liantuo Formation represents a warm-damp interglacial period, and the top Liantuo Formation and the Nantuo Formation represent an arid-frigid cold ice period again. According to the present result, a new division and correlation of the Nanhua System in the Yangtze Platform are suggested here.
中文关键词	化学蚀变指数(CIA) ; 钾交代 ; 成分变化指数(ICV) ; 新元古代 ; 南华系 ; 莲沱组
英文关键词	chemical index of alteration (CIA) potassium replacements index of compositional variability (ICV) Neoproterozoic Nanhua System Liantuo Formation
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:2419395
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/219574
作者单位	1.(北京)中国地质大学, 北京 100083, 中国; 2.中国地质科学院地质研究所, 北京 100037, 中国
推荐引用方式 GB/T 7714	王自强,尹崇玉,高林志,等. 宜昌三斗坪地区南华系化学蚀变指数特征及南华系划分、对比的讨论[J],2006,52(5):577-585.
APA	王自强,尹崇玉,高林志,唐烽,柳永清,&刘鹏举.(2006).宜昌三斗坪地区南华系化学蚀变指数特征及南华系划分、对比的讨论.,52(5),577-585.
MLA	王自强,et al."宜昌三斗坪地区南华系化学蚀变指数特征及南华系划分、对比的讨论".52.5(2006):577-585.