杨晓东^1,2,,
赵希涛^1,3,
吴中海^1,,,
刘锋¹,
周春景¹
1. 自然资源部新构造运动与地质灾害重点实验室, 中国地质科学院地质力学研究所, 北京 100081
2. 中国地质大学(北京)地球科学与资源学院, 北京 100083
3. 中国科学院地质与地球物理研究所, 北京 100029

基金项目: 中国地质调查局项目（批准号：DD20160268）资助


详细信息

作者简介: 杨晓东, 男, 27岁, 硕士研究生, 第四纪地质与新构造研究, E-mail:dong6015@126.com

通讯作者: 吴中海, E-mail:wuzhonghai@geomech.ac.cn, wzhh4488@sina.com

中图分类号: P597⁺.3

收稿日期:2017-12-08
修回日期:2018-03-02
刊出日期:2018-05-30

Ar-Ar geochronology of basalts in Liuhe area, Nanjing and its geological significance

Yang Xiaodong^1,2,,
Zhao Xitao^1,3,
Wu Zhonghai^1,,,
Liu Feng¹,
Zhou Chunjing¹
1. Key Laboratory of Neotectonic Movement and Geohazards, Ministry of Natural Resources, Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081
2. College of Earth Science and Resources, China University of Geosciences(Beijing), Beijing 100083
3. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029


More Information

Corresponding author: Wu Zhonghai,E-mail:wuzhonghai@geomech.ac.cn

MSC: P597⁺.3

--> Received Date: 08 December 2017
Revised Date: 02 March 2018
Publish Date: 30 May 2018


摘要
摘要:江苏南京六合地区广泛分布着新近纪的玄武岩火山锥和古长江三角洲砂砾层，前者有的直接覆盖在古长江三角洲的砂砾层之上，有的则被后者所切割覆盖，而两者之间的关系和时代对于认识古长江三角洲的形成演化具有重要意义。利用⁴⁰Ar-³⁹Ar法对采集于六合地区奶山、方山和灵岩山的玄武岩进行年龄测定后发现，奶山玄武岩的形成时代为约16.90±0.37 Ma，而六合方山与灵岩山的形成时代分别为约9.55±0.03 Ma和10.43±0.03 Ma。新的年龄结果证实，南京六合地区在中新世期间至少发生了早、晚两期火山喷溢活动，它们分别是距今16~17 Ma和9~10 Ma，并在这两期玄武岩活动期间广泛发育了一套古长江三角洲沉积。
关键词: 古长江三角洲/
南京六合/
新近纪火山/
Ar-Ar测年

Abstract:The Neogene basaltic volcanic cone and the paleo Changjiang River delta sand gravel layer are widely distributed in Liuhe area, Nanjing, Jiangsu. And it is located in the lower Changjiang plate which is on the east side of the Tanlu Fault Zone. Some basalts directly overlay above the gravel layer of the ancient Changjiang River delta, while some are cut and covered by the latter. The relationship between the two and the age of formation is of great significance to the understanding of the formation and evolution of the ancient Changjiang River delta. In this paper, the ⁴⁰Ar-³⁹Ar method was used to determine the age of the basalts in the Nai Mountain(32°17'59.16″N, 119°00'24.69″E), the Liuhe Fangshan(32°18'29.07″N, 118°59'20.80″E) and the Lingyan Mountain(32°17'49.69″N, 118°53'24.95″E), which is located in the ancient Changjiang River alluvial plain in southeast of Liuhe. In the landscape, Fangshan and Lingyan Mountain are truncated conical shape, and the basalts overlay above the gravel layer of the ancient Changjiang River. Nai Mountain is a combination of two cone hills which leaned on each other, and it's basalt is cut by the ancient sand gravel layer of the Changjiang River. The samples were selected from fresh appearance from the three mountains, hard texture, and massive structure. The samples were processed and tested at the Argon Chronology Laboratory of the Institute of Geology, Oceanology and Atmospheric Sciences, Oregon State University, United States. The Ar-Ar result shows that, the age of the basalt in Nai Mountain is 16.90±0.37 Ma, which is obtained for the first time in the history. Liuhe Fangshan and Lingyan Mountain got a flat age spectrum, which is 9.55±0.03 Ma and 10.43±0.03 Ma, which is approximately close to the results of previous K-Ar dating. The new age result indicates that, there are at least two volcano eruptions in Miocene in Liuhe area, Nai Mountain basalt is earlier formed than which in Liuhe Fangshan and Lingyan Mountain. Combined with previous research results, the Neogene volcanic activity era in Liuhe area has been more precise, and the two periods of volcanic activity are limited to about 16~17 Ma and 9~10 Ma. There is still need for further research on whether there are third periods of volcanic activity during Pliocene. During the period of the two phases of basalt, a set of paleo Changjiang River delta deposits were widely developed in this area. The Ar-Ar geochronology is helpful for the study of volcanic activity and the stages of gravel formation and the evolution of the ancient Changjiang River.
Key words:the ancient Changjiang River delta/
Liuhe area/
Neogene volcano/
Ar-Ar



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