Present-day temperatures of magma chambers in the crust beneath Ninger volcanic field, southwestern China: Estimation from CO2-CH4 carbon isotope geothermometer

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	Present-day temperatures of magma chambers in the crust beneath Ninger volcanic field, southwestern China: Estimation from CO2-CH4 carbon isotope geothermometer
	Zhao CiPing 1; Wang Yun 1; Zhou Zhi 1; Li ZhongPing 2; Xing LanTian 2
刊名	ACTA PETROLOGICA SINICA
	2017
卷号	33 期号:1 页码:231-249
关键词	Magma Temperature Carbon Isotopic Geothermometer Co2 And Ch4 Thermal Spring Gases Ninger Volcanic Field
ISSN号	1000-0569
文献子类	Article
英文摘要	Temperature is an important physical parameter of magma. To access and monitor temperature parameter of magma favors better understanding variations of the physical and chemical properties and behavior of magma, the evaluation of activity and eruption risk of a volcano. Volcanic magma and hydrothermal system enrich carbon bearing gases. Therefore the carbon isotopic thermometers can be employed to acquire the magma temperature of subsurface dormant volcano. Here we conduct 2 years of continuous and 2 times of parallel observation on carbon isotope composition of CO2 and CH4 of 4 thermal springs in highest strength of ground geothermal anomaly area in Ninger Volcanic Field (NVF). Using observational data, we identify whether CO2 and CH4 gases come from magma, and judge whether carbon isotope fractionation between CO2 and CH4 attain equilibrium. Using Horita CO2-CH4 carbon isotope equilibrium fractionation equation we calculate the source temperature of volcanic gases escape from the NVF. Our results show that, of 4 thermal springs in NVF, CO2 and CH4 from 1 are of non-magmatic origin, but that from the other 3 are mainly of magmatic origin, and that after excluding non-magmatic origin data, carbon isotope fractionation between CO2 and CH4 of the rest data attain equilibrium according delta-Delta plot method, and that gases source temperature of CO2 and CH4 of these 3 thermal springs are 425 similar to 475 degrees C, 941 similar to 995 degrees C and 1179 similar to 1578 degrees C, respectively. Combining our data and the uppermost crust temperature field results, we conclude that, there exist 2 magma chambers in NVF at present day, which located south to Ninger Volcano and north to Tongguan Volcano, respectively, that the temperature of Ninger magma chamber is up to 1179 similar to 1578 degrees C, that of Tongguan magma chamber, 941 similar to 995 degrees C, which reach to rhyolite (600 similar to 900 degrees C), andesites (800 similar to 1100 degrees C) and the basaltic magma (1000 similar to 1250 degrees C) formation temperature, and that intensive magnitude 6 earthquake cluster activity in space in Simao-Puer seismic zone can be explained by stronger activity level of Ninger magma chamber. The delta-Delta plot guidelines of determining the carbon isotope fractionation equilibrium between CO2 and CH4 should be amended as follows: under the conditions that the sign of the slope of the two fitting lines keep always opposite, the delta C-13(CO2) Delta(CO2-CH4) fitting straight line and the delta(13) C-CH4-Delta(CO2-CH4) one should intersect near the delta-axis with intercept difference Delta(b) <= 0.16.
WOS关键词	EQUATION-OF-STATE ; MOLECULAR-DYNAMICS SIMULATION ; SATSUMA-IWOJIMA ; HYDROTHERMAL SYSTEMS ; CH4-CO2-H2O SYSTEM ; GAS-DISCHARGES ; 10 GPA ; CO2 ; METHANE ; CH4
WOS研究方向	Geology
语种	英语
出版者	SCIENCE PRESS
WOS记录号	WOS:000393257900019
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/53105]
专题	地质与地球物理研究所_兰州油气中心
通讯作者	Zhao CiPing
作者单位	1.Earthquake Adm Yunnan Prov, Kunming 650124, Peoples R China 2.Chinese Acad Sci, Inst Geol & Geophys, Lanzhou Ctr Oil & Gas Resources, Lanzhou 730000, Peoples R China
推荐引用方式 GB/T 7714	Zhao CiPing,Wang Yun,Zhou Zhi,et al. Present-day temperatures of magma chambers in the crust beneath Ninger volcanic field, southwestern China: Estimation from CO2-CH4 carbon isotope geothermometer[J]. ACTA PETROLOGICA SINICA,2017,33(1):231-249.
APA	Zhao CiPing,Wang Yun,Zhou Zhi,Li ZhongPing,&Xing LanTian.(2017).Present-day temperatures of magma chambers in the crust beneath Ninger volcanic field, southwestern China: Estimation from CO2-CH4 carbon isotope geothermometer.ACTA PETROLOGICA SINICA,33(1),231-249.
MLA	Zhao CiPing,et al."Present-day temperatures of magma chambers in the crust beneath Ninger volcanic field, southwestern China: Estimation from CO2-CH4 carbon isotope geothermometer".ACTA PETROLOGICA SINICA 33.1(2017):231-249.