收稿日期: 2013-05-12
修回日期: 2013-07-31
网络出版日期: 2013-09-10
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
Received date: 2013-05-12
Revised date: 2013-07-31
Online published: 2013-09-10
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
辛补社 , 杨华 , 王多云 , 付金华 , 姚泾利 , 罗安湘 , 张瑜 . 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[J]. 地球科学进展, 2013 , 28(9) : 1043 -1048 . DOI: 10.11867/j.issn.1001-8166.2013.09.1043
Using zircon SHRIMP U-Pb dating method in this paper, we conduct the SHRIMP UPb 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.
[1]Tong Zaisan, Shen Guanglong, Wu Anbin, et al. Discovery of several volcanic rocks from Jingyuan coal field in the Baojishan mining area of Triassic strata[J]. Journal of Lanzhou University (Natural Sciences), 1987, 26(2): 135-136.[佟再三，沈光隆，武安斌，等. 靖远煤田宝积山矿区三叠系发现多层火山碎屑岩[J]. 兰州大学学报：自然科学版，1987,26（2）：135-136.]
[2]Sun Bainian, Xu Jinglong. Discovery of plant fossils from Baojishan-Yaoci mining area of Triassic volcanic rocks[J]. Journal of Lanzhou University (Natural Sciences), 1988, 24(4): 166.[孙柏年，许敬龙. 宝积山—窑磁矿区三叠系火山岩中植物化石的发现[J]. 兰州大学学报：自然科学版，1988,24（4）：166.]
[3]Sun Bainian, Guo Yuansheng, Ma Jinlong, et al. The Triassic strata of the Lenglongling of Tianzhu in the east part of the Northern Qilian Mountains[J]. Journal of Lanzhou University (Natural Sciences), 1996, 32(3): 132-136.[孙柏年，郭原生，马锦龙，等. 北祁连东段天祝冷龙岭一带三叠纪地层[J]. 兰州大学学报：自然科学版，1996,32（3）：132-136.]
[4]Xie Wanhua, Gu Zugang. The late Triassic flora and coal prospects at Baojishan, Jingyuan, Gansu[J]. Regional Geology of China, 1988, 4: 358-361.[谢万华，谷祖刚. 甘肃靖远县宝积山晚三叠世植物群组合与含煤远景初探[J]. 中国区域地质，1988,4:358-361.]
[5]Han Zifang, Shen Guanglong. Stratigraphic primary division and correlation of Triassic strata at Dingjiayao area of Baiyin district of Lanzhou City[J]. Northwestern Geology, 1978,2: 38-46.[韩子芳，沈光隆. 兰州市白银区丁家窑一带三叠纪地层的初步划分与对比[J]. 西北地质，1978,2:38-46.]
[6]Xin Bushe, Yang Hua, Fu Jinhua, et al. SHRIMP U-Pb zircon age and its stratigraphic significance of tuff at the bottom of the Upper Triassic Nanying’er Group, Mountain Baoji area, Jingyuan County, Gansu Province[J]. Geological Review, 2013, 59(2): 267-273.[辛补社，杨华，付金华，等. 甘肃靖远宝积山地区上三叠统南营儿群底部凝灰岩锆石SHRIMP U-Pb年龄及其地层学意义[J]. 地质论评，2013,59（2）：267-273.]
[7]Feng Yimin, He Shiping. The Geotectonics and Orogeny of Qilian Mountain[M]. Beijing: Geological Publishing House, 1996.[冯益民，何世平. 祁连山大地构造与造山作用[M]. 北京：地质出版社，1996.]
[8]Williams I S, Claesson S. Isotopic evidence for the Precambrian provenance and Caledonian metamorphism of high grade paragneisses from the Seve Nappes, Scandinavian Caledonides[J]. Contributions to Mineralogy and Petrology, 1987, 97(2): 205-217.
[9]Compston W, Williams I S, Kirschvink J L, et al. Zircon U-Pb ages for the Early Cambrian time-scale[J]. Journal of the Geological Society, 1992, 149(2): 171-184.
[10]Ludwig K R. User’s Manual for Lsoplot 3.70: A Geochronological Toolkit for Microsoft Excel[Z]. Berkeley Geochronology Center Special Publication No.4, 2008.
[11]Wu Yuanbao, Zheng Yongfei. Mineralogical study of zircon origin and constraint interpretation for the U-Pb ages of zircon[J]. Chinese Science Bulletin, 2004, 49(16): 1 589-1 604.[吴元保，郑永飞. 锆石成因矿物学研究及其对U-Pb年龄解释的制约[J]. 科学通报，2004,49（16）：1 589-1 604.]
[12]Mietto P, Manfrin S, Preto N, et al. The Global Boundary Stratotype Section and Point(GSSP) of the Carnian stage(Late Triassic) at Prati di Stuores/stuores Wiesen Section(Southern Alps, NE Italy)[J]. Episodes, 2012,35(3): 414-430.
[13]Brack P, Rieber H, Nicora A, et al. The Global boundary Stratotype Section and Point(GSSP) of the Ladinian Stage(Middle Triassic) at Bagolino(Southern Alps, Northern Italy) and its implications for the Triassic time scale[J]. Episodes, 2005,28(4): 233-244.
[14]Du Bao’an. Middle Triassic palynological assemblage in the Wangjiashan Basin of Jingyuan, Gansu and its stratigraphical significance[J]. Acta Botanica Sinica, 1985, 27(5): 538-544.[杜宝安. 甘肃靖远王家山中三叠世孢粉组合及其地层意义[J]. 植物学报，1985,27（5）：538-544.]
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