Zircon U-Pb dating of the mafic lava from Wudaoshimen, Hexigten, Inner Mongolia and its geological significance

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	Zircon U-Pb dating of the mafic lava from Wudaoshimen, Hexigten, Inner Mongolia and its geological significance
	Wang YanYang 1; Xu Bei 1; Cheng ShengDong 1; Liao Wen 1; Shao Jun 2; Wang Yan 2
刊名	ACTA PETROLOGICA SINICA
	2014
卷号	30 期号:7 页码:2055-2062
关键词	OROGENIC BELT NORTH CHINA EVOLUTION GEOCHRONOLOGY SUBDUCTION COLLISION SUTURE Dashizhai Formation Pillow basalts Zircon U-Pb age Xing' an-Mongolian orogenic belt
ISSN号	1000-0569
其他题名	Zircon U-Pb dating of the mafic lava from Wudaoshimen, Hexigten, Inner Mongolia and its geological significance
英文摘要	-A series of volcanic-sedimentary rocks, composed of gray-green basalts, pillow basalts in lower part and siliceous siltstone in upper part, was recognized in Wudaoshimen area, Hexigten Banner, Inner Mongolia. Previous studies considered them as part of the Early Paleozoic ophiolite suite. In this paper, a pillow basalt sample was collected to date U-Pb ages of zircons by using LAICP-MS analytical techniques. Existed south of the Wudaoshimen dam, the pillows are irregular ellipsoidal with long axis ranging from 0. 4 1. Om, and have obvious condensation rims and little pores inside. The pillow basalt sample display typical intergranular texture with plenty of narrow-strip feldspar and some tiny pyroxene under microscope. Most zircons are colorless, transparent, and euhedral to subhedral in shape. Cathodoluminescene (CL) imaging shows most of them have oscillatory zones. Combined with their high Th/U ratios (> O. 1, except for one spot of O. 08), it is suggested that these zircons are of igneous origin. The 31 zircon analyses are concordant, and show four groups; 261 290Ma (group A, n =15), 301 345Ma (group B, n =5), 446 572Ma (group C, n =6) and 763 948Ma (group D, n =5), respectively. Group A zircons are euhedral and columnar with length: width ratios of 2 : 1 3 : 1, and display typical widely-spaced oscillatory zoning, which indicates they crystallized at relatively high temperature. Fifteen zircon analyses yield a concordant age of 277 3Ma (MSWD = 0. 02), representing that the Wudaoshimen pillow basalts formed in the late Early-Permian and belong to the Dashizhai Formation. Group B zircons are euhedral and columnar, while group C and D zircons are subhedral-euhedral and granular, respectively. Furthermore, most of these three group zircons display closely-spaced concentric oscillatory zoning. The remarkable differences between group A and the other three groups suggest different source. Combined with the lack of magmatic rims with age of 270 280Ma in older zircons, they may be more likely captured from the wall rocks when mafic magma intruding. Thus the scattered ages of 301 345Ma, 446 572Ma and 763 948Ma reflect information of the wall rocks. The Wudaoshimen pillow basalts were regarded as part of the Early Paleozoic ophiolites in previous research. However, based on the concordant age of 277 3Ma, we consider that they formed in the late Early-Permian. Because no ultramafic rocks have been found in research area, we suggest they are not part of ophiolite suite. The three group older captured zircons in the Wudaoshimen pillow basalts display that they formed in a continental crust with the Neoproterozoic to Paleozoic basement during an intraplate extension.
语种	英语
CSCD记录号	CSCD:5188635
内容类型	期刊论文
源URL	[http://ir.imr.ac.cn/handle/321006/144935]
专题	金属研究所_中国科学院金属研究所
作者单位	1.北京大学 2.中国科学院金属研究所
推荐引用方式 GB/T 7714	Wang YanYang,Xu Bei,Cheng ShengDong,et al. Zircon U-Pb dating of the mafic lava from Wudaoshimen, Hexigten, Inner Mongolia and its geological significance[J]. ACTA PETROLOGICA SINICA,2014,30(7):2055-2062.
APA	Wang YanYang,Xu Bei,Cheng ShengDong,Liao Wen,Shao Jun,&Wang Yan.(2014).Zircon U-Pb dating of the mafic lava from Wudaoshimen, Hexigten, Inner Mongolia and its geological significance.ACTA PETROLOGICA SINICA,30(7),2055-2062.
MLA	Wang YanYang,et al."Zircon U-Pb dating of the mafic lava from Wudaoshimen, Hexigten, Inner Mongolia and its geological significance".ACTA PETROLOGICA SINICA 30.7(2014):2055-2062.