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黔东北地区南华系两界河组CIA指数特征及意义
郑杰1,阳正熙2,刘石磊2,安显银2,桑永恒2,马健飞2
0
(1. 成都理工大学, 四川 成都 610059;
2. 中国地质调查局成都地质调查中心, 四川 成都 610081)
摘要:
化学蚀变指数(CIA)是判断源岩风化程度的化学指标。通过分析黔东北地区苗哨溪剖面两界河组的CIA特征,为讨论其古气候特征提供地球化学方面的依据。结果表明,两界河组CIA值介于55.48~89.33之间,均值为72.49,除极个别数值为55.48、89.33之外,其它数值皆介于65~75之间,指示两界河组具有温暖湿润的古气候特征。通过综合分析两界河组岩石组合、沉积构造及古气候特征,认为两界河组为间冰期沉积。在此基础上,结合最新同位素年代学数据,认为其可与富禄组中上部进行对比。
关键词:  黔东北  南华系  两界河组  化学蚀变指数CIA
DOI:
投稿时间:2018-07-08修订日期:2018-10-12
基金项目:Sturtian冰期区域性海侵事件启动时间及其性质研究-以黔东北地区两界河组为例(41802137);及中国地质调查局项目(DD20160018)联合资助
The chemical alteration indexes and their significance for the Nanhuan Liangjiehe Formation in northeastern Guizhou
ZHENG Jie1, YANG Zhengxi2, LIU Shilei2, AN Xianyin2, SANG Yongheng2, MA Jianfei2
(1. Chengdu University of Technology, Chengdu 610059, Sichuan, China;
2. Chengdu Center, China Geological Survey, Chengdu 610081, Sichuan, China)
Abstract:
There has been much debated recently concerning the issue whether or not the Nanhuan Liangjiehe Formation may be classified into the interglacial deposits. The values of chemical alteration index (CIA) for the Liangjiehe Formation in the Miaoshaoxi section, northeastern Guizhou may directly provide geochemical evidence for the approaches to the palaeoclimatological features in this region. The values of chemical alteration index presented in this study generally vary from 55.48 to 89.33, with an average of 72.49. Except the values 55.48 and 89.33, all the other ones range between 65 and 75, indicating the warm and humid palaeoclimatic conditions during the deposition of the Liangjiehe Formation. The integration of rock assemblages, sedimentary structures and palaeoclimatological features show that the Liangjiehe Formation should be assigned to the interglacial deposits, and may be correlated to the middle and upper parts of the Fulu Formation.
Key words:  northeastern Guizhou  Nanhuan  Liangjiehe Formation  chemical alteration index(CIA)

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