甘肃靖远王家山地区凝灰岩锆石U-Pb年龄及地层对比意义

doi:10.11867/j.issn.1001-8166.2013.09.1043

地球科学进展 ›› 2013, Vol. 28 ›› Issue (9): 1043 -1048. doi: 10.11867/j.issn.1001-8166.2013.09.1043

辛补社 ¹，杨华 ^2,3，王多云 ^1*，付金华 ^2,3，姚泾利 ^3,4，罗安湘 ^3,4，张瑜 ¹

1.北京师范大学资源学院，北京 100875；2.中国石油长庆油田公司，陕西西安 710018；3.低渗透油气田勘探开发国家工程实验室，陕西西安 710018；4.中国石油长庆油田公司勘探开发研究院，陕西西安 710018

收稿日期:2013-05-12 修回日期:2013-07-31 出版日期:2013-09-10
通讯作者: 王多云（1956-），男，甘肃民勤人，教授，主要从事层序地层学和油气区地球物理探勘研究.E-mail:wdy@bnu.edu.cn E-mail:wdy@bnu.edu.cn
基金资助:
国家“十二五”科技重大专项“鄂尔多斯盆地南缘中生代构造演化及其对沉积体系控制作用”（编号：2011ZX05044）资助

SHRIMP U-Pb Age and Its Stratigraphic Significance of Tuff at the Baojishan Area, Jingyuan County, Gansu Province

Xin Bushe ¹, Yang Hua ^2,3, Wang Duoyun ¹, Fu Jinhua ^2,3, Yao Jingli ^3,4, Luo Anxiang ^3,4, Zhang Yu ¹

1.College of Resource Science and Technology, Beijing Normal University, Beijing 100875, China; 2.PetroChina Changqing Oilfield Company, Xi’an 710018, China; 3. National Engineering Laboratory of Exploration and Development of Low-Permeability Oil and Gas Field, Xi’an 710018, China;
4. Exploration and Development Research Institute of PetroChina Changqing Oilfield Company, Xi’an 710018, China

Received:2013-05-12 Revised:2013-07-31 Online:2013-09-10 Published:2013-09-10

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利用锆石SHRIMP U-Pb定年方法，对甘肃靖远王家山地区南营儿群底部新发现的凝灰岩进行了锆石U-Pb定年分析，获得一组²⁰⁶Pb/²³⁸U加权平均年龄为(244.9±2.8) Ma。结合凝灰岩锆石阴极发光特征和锆石Th/U比值，认为该组年龄代表了凝灰岩的沉积年龄。这一高精度、高可置信度的研究成果充分说明南营儿群的底部存在中三叠世早期地层，建议将南营儿群底部的凝灰岩及其以下地层划归中三叠统丁家窑组。同时，也证实靖远王家山凝灰岩与宝积山凝灰岩为同一期火山喷发的沉积产物，该凝灰岩层可以作为区域地层划分和对比的标志层。上述研究成果对河西走廊地区中、上三叠统的划分与对比以及最终建立北方陆相三叠纪年代地层对比格架，都有一定的地层学意义。

关键词: 靖远王家山, 凝灰岩, 锆石SHRIMP U-Pb定年, 地层学意义

Using zircon SHRIMP U-Pb dating method in this paper, we conduct the SHRIMP UPb ages of tuff at the bottom of the Nanying’er Group, Wangjiashan area, Jingyuan County, Gansu Province and acquire a set of weighted average age of (244.9±2.8)Ma. Combined with the feature of Cathodoluminescence images and Th/U specific value of zircon, we believe that the sedimentary age of Wangjiashan tuff is (244.9±2.8)Ma. High precision and high confidence isotopic age data fully demonstrate that the bottom of Nanying’er Group exists with the early of middle Triassic strata. The author proposes that the Wangjiashan tuff and its hereinafter strata should be incorporated in Dingjiayao Formation. Meanwhile, it can be confirmed that the Wangjiashan Tuff and the Baojishan tuff are the deposition product of the same volcanic eruption. It can be used as a marker bed of the regional stratigraphic division and correlation. The above research results are beneficial for the upper and middle Triassic stratigraphic division and correlation of Hexi corridor region, and its stratigraphic significance for the final establishment of Triassic chronostratigraphic division and correlation framework of China’s northern continental strata.

Key words: Tuff, Zircon SHRIMP U-Pb age, Stratigraphic significance, Wangjiashan area of Jingyuan County

中图分类号:

P535

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