摘要
稀土元素因其化学性质稳定已成为研究湖泊沉积物的物源、古环境和古气候等变化的良好示踪剂。笔者采集江陵凹陷GK2井古新统沙市组上段岩芯样品21件、新沟嘴组下段岩芯样品39件,并采用电感耦合等离子体质谱技术对其稀土元素进行测试分析。结果表明：∑REE为67.941-284.385μg/g,平均值为174.63μg/g,高于全球平均大陆上地壳值,稍大于北美页岩。样品的δEu值为0.61-0.89,平均为0.71,中度Eu异常;δCe值为0.88-0.99,平均为0.93,Ce微负异常。稀土元素的配分模式为LREE、HREE分异明显,LREE呈现右倾,HREE较为平坦,富集LREE,HREE相对亏损。δEu、δCe值的变化表明当时的水体为还原环境;∑REE和（La/Yb）N值的变化表明,从沙市组上段到新沟嘴组下段气候由干热变得相对暖湿;物源以沉积岩为主,也有部分可能来自花岗岩和玄武岩。黄陵隆起的隆升剥蚀过程和东秦岭、华容地区花岗岩稀土元素配分模式与江陵凹陷样品的对比分析结果,表明东秦岭、黄陵隆起和华容地区花岗岩在古新世时期可能向江陵凹陷提供了物源。
Rare earth elements （REE） with stable geochemical characteristics are good indicators for studying the provenance, paleoenvironment and paleoclimate of lake sediments, and thus have important research significance. The authors collected 21 core samples from the upper member of Paleocene Shashi Formation in GK2 well of the Jiangling Depression and 39 samples from the lower member of Xingouzui Formation, and used ICP-MS method to determine the values of rare earth elements of the samples. According to the results achieved, ∑REE values range from 67. 941 × 10 - 6 to 284. 385 × 10 - 6 with an average of 174.63 × 10- 6, higher than values of the upper continental crust and the North American Shale Composite. The 3Eu values vary in the range of 0.61- 0.89, 0.71 on average, and the samples are lack of Eu; the samples have slightly negative Ce anomaly, and the 3Ce values are in the range of 0.88--0.99, with an average of 0.93. The rare earth element patterns indicate that the LREE is rich and the HREE is poor, and the HREE patterns are flat. The lack of Eu and Ce shows that the an- cient water was reductive. According to the change of the values of ~REE and （La/Yb）N, it is concluded that the climate became more warm and humid from the upper member of Shashi Formation to the lower member of Xingouzui Formation, and the provenance was mainly derived from sedimentary rocks as well as some granites and basalts. On the basis of the study of the uplifting process of Huangling dome and the comparative study of the rare earth element patterns of the granites of East Qinling and Huarong dome, the authors hold that the granites of East Qinling, Huangling and Huarong dome might have provided the Jiiang Depression with the provenances.
出处
《矿床地质》
CAS
CSCD
北大核心
2014年第5期1057-1068,共12页
Mineral Deposits
基金
973项目(编号:2011CB403007)
中央级公益性科研院所基本科研业务费专项(编号:K1415)
中国地质大调查项目(编号:12120114051901)
国家自然科学基金青年基金(编号:41202059)联合资助
关键词
地球化学
江陵凹陷
稀土元素
氧化-还原
古气候
物源
geochemistry, Jiangling Depression, rare earth elements, oxidation-reduction, paleoclimate,provenance
