中国K-Ar法地质年龄标准物质ZBH-15黑云母的研制  

Intercalibration of the ZBH-15 Biotite Reference Material Utilized for K-Ar and ^(40)Ar-^(39)Ar Isotopic Dating in China

作　　者：桑海清[1] 王非[1] 贺怀宇[1] 王英兰[1] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029

出　　处：《矿物岩石地球化学通报》2006年第3期201-217,共17页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：岩石圈演化国家重点实验室基金资助项目

摘　　要：为满足K-Ar定年中K和40Ar*分析的质量监控及Ar-Ar定年时中子通量监测的需要,我国氩同位素专家研制了一种K-Ar法年龄标准物质———采自北京房山花岗闪长岩体的ZBH-15黑云母。其40Ar/39Ar阶段加热实验结果表明,年龄谱平坦,39Ar析出量高达98.3%。坪年龄为132.2±0.2 Ma,总气体年龄为131.3±0.5 Ma,证明该黑云母结晶以后未受过热扰动。36Ar/40Ar-39Ar/40Ar反等时线年龄为132.3±0.8 Ma,40Ar/36Ar初始值为293.9±1.4,与大气氩丰度比值(295.5±0.5)处于同一范围,表明该样品不含过剩氩。在0.05显著性水平下经统计学检验,证明K和40Ar*的F值小于F临界值,说明该样品是均匀的。国内外7个实验室参加了K和40Ar*的定值分析。用同位素稀释法测定40Ar*含量,火焰光度法测定K含量。统计检验结果显示,K和40Ar*的全部定值数据服从正态分布并具等精度。定值分析结果的认定值及不确定度分别为:40Ar*=(1.814±0.014)×10-9mol/g,K=7.59%±0.02%,K-Ar年龄t=132.8±1.3 Ma(2σ)。此标准物质纯度为98.8%,粒度为0.15~0.25 mm,重量为2070 g,缩分成225瓶,每瓶9.2 g。可供我国K-Ar和Ar-Ar法实验室使用43 a。ZBH-15 biotite has been successfully studied for K-Ar and ^40Ar-^39 Ar dating purpose by argon isotope chronologist of Chinese. The biotite, as fist K Ar age standard material of China, were separated from Fangshan granodiorite complex in the southwest of Beijing, which occupies an area of 47 km^2. About 2070 g of pure ZBH-15 biotite was obtained at the 0.15-0.25 mm fraction. The purity is about 99.8%. Following mixing, the ZBH-15 biotite was divided into 15 jars about 138 g each. Each jar sample was further subdivided into 15 aliquots about 9.2 g each （total 225 aliquots）. ^40Ar-^39Ar age spectrum of ZBH-15 biotite indicates that the biotite has remained undisturbed since its crystallization. The plateau age （3-13 steps） and total gases age （1-13 steps） are 132.2±0.2Ma and 131.3±0.5 Ma. The argon extraction occurs mainly between 750-1400℃, and about 98.3% radiogenic ^40Ar can be released at that temperature rang. From the data of 3-14 steps heating the isochron age and the initial ^40Ar/^36Ar ration of the biotite are 132.3±0.8 Ma and 293. 9 ± 1.4 Ma, respectively. The correlation coefficient and MSWD in the isochron diagram are 0. 99999 and 0.3, respectively. The homogeneity tests were performed in Ar isotopic laboratory of Institute of Geology and Geophysics, Chinese Academy of Science. The sample weights are 15 mg for ^40Ar^＊ and 60 mg for K. Statistical estimate of analytical data show that F values of K and ^40Ar^＊ are less in calibrations of ^40Ar^＊ and K of ZBH 15 biotite. K-calibrations have been done with flame photometry and atomic absorption. The calibrations of ^40 Ar^＊ were performed by isotopic dilution method, ^38Ar spike and ,^40Ar-^39 Ar techniques. The Grubbs and Dixon tests indicate that there is no outlier in all data from 8 laboratories. The calculations of skewness and kurtosis coefficients, and the Cochran isoprecision indicate that all data of K and ^40Ar^＊ , obey a normal distribution. The certificate values for ^40Ar^＊ and K of ZBH 15 biotite are calculated

关 键 词：ZBH-15黑云母 标准物质 均匀性检验 K和^40Ar^＊的定值分析 统计学检验 K-Ar和Ar-Ar定年 

分 类 号：P597.3[天文地球—地球化学]