Laser fusion Ar-40/Ar-39 dating on young volcanic rocks

	Laser fusion Ar-40/Ar-39 dating on young volcanic rocks
	Zhou Jing 1; Ji JianQing 1; Deino, Alan 2; Gong JunFeng 1; Han BaoFu 1; Tu JiYao 1; Sang HaiQing 3; Xu JianGuang 1
刊名	ACTA PETROLOGICA SINICA
	2013-08-01
卷号	29 期号:8 页码:2811-2825
关键词	Laser Ar-40/(39) Ar Young And Modern Volcanic Rocks Neutron-flux Monitors (Standards) Irradiated Parameters Phenocryst-matrix Isochron
ISSN号	1000-0569
文献子类	Article
英文摘要	It is extremely difficult to date young volcanic rocks. Accurate Ar-40/Ar-39 dating research and practice of young volcanic rocks in China put forward several notable and important points during the process of Ar-40/(39) Ar dating for young volcanic rocks. Because of the low background level, small sample quantity, and high sensitivity of modern noble gas isotope mass spectrometry device, laser ablation Ar-40/Ar-39 dating technique has been used in depth application in volcanic rocks dating. With the laser in Ar-40/Ar-39 dating of young and modern volcanic rocks, the discrepancy of Nier value and initial argon isotope ratio in Quaternary samples may cause a remarkable deviation between K-Ar apparent age and Ar-40/Ar-39 apparent age. The deviation show exponential increase for samples younger than 0. 2Ma, but it is not so notable for samples older than 2Ma. There out, the boundary of young and modern volcanic rocks, which is applied to Ar-40/Ar-39 system, is assigned at 0. 2Ma: rocks aged 2 similar to 0. 2Ma is defined as young volcanic rock, while rocks aged younger than 0. 2Ma is defined as modern volcanic rock. The phenocrysts, which are from different argon isotope fractionation system, should be rejected from the sample during Ar-40/Ar-39 dating. According to rock texture and grain size of mineral, the matrix should be picked with ideal grain size. In normal cases, about 0. 2mm (or 60 similar to 80 mesh) is recommended; Cooling time after irradiation of fast neutron reactor should not be no more than three months, or else it may cause an error on Ar-37 measurement, and consequently on final results. As neutron-flux monitor, standards should be characteristic of high homogeneity during laser Ar-40/Ar-39 dating. In calibrating the international and domestic standards we have, we find that SB-778-Bi, Bern4M and BT-1 can be ideal standard samples with good homogeneity. We also find that the isochron age calculated from the laser Ar-40/Ar-39 data of the phenocryst and matrix, which were cooled and crystallized at the same time during volcanic eruption, is an objective and precise age. For volcanic rocks with almost the same crystallization time, the same magma source, and perfect argon-argon closed system, phenocryst-matrix isochron method can be adopted to gain more precise and reliable results.
WOS关键词	K-AR ; EXCESS ARGON ; AGE-DETERMINATION ; ALDER-CREEK ; STANDARDS ; INTERCALIBRATION ; GEOCHRONOLOGY ; CALIBRATION ; CALIFORNIA ; CANYON
WOS研究方向	Geology
语种	英语
出版者	SCIENCE PRESS
WOS记录号	WOS:000323689100017
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/86328]
专题	中国科学院地质与地球物理研究所
通讯作者	Zhou Jing
作者单位	1.Peking Univ, Sch Earth & Space Sci, Lab Orogen Belts & Crustal Evolut, Beijing 100871, Peoples R China 2.Berkeley Geochronol Ctr, Berkeley, CA 94709 USA 3.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China
推荐引用方式 GB/T 7714	Zhou Jing,Ji JianQing,Deino, Alan,et al. Laser fusion Ar-40/Ar-39 dating on young volcanic rocks[J]. ACTA PETROLOGICA SINICA,2013,29(8):2811-2825.
APA	Zhou Jing.,Ji JianQing.,Deino, Alan.,Gong JunFeng.,Han BaoFu.,...&Xu JianGuang.(2013).Laser fusion Ar-40/Ar-39 dating on young volcanic rocks.ACTA PETROLOGICA SINICA,29(8),2811-2825.
MLA	Zhou Jing,et al."Laser fusion Ar-40/Ar-39 dating on young volcanic rocks".ACTA PETROLOGICA SINICA 29.8(2013):2811-2825.