应用稳定同位素示踪琥珀的产地

Stable Isotopes Tracing of Origin of Ambers

  • 摘要: 利用稳定同位素比值质谱仪(IRMS)对波罗的海琥珀、多米尼加琥珀、墨西哥琥珀、缅甸琥珀及不同产地的柯巴树脂的13C,D,18 O稳定同位素进行了高精度测定。研究结果表明:(1)不同产地琥珀的δ13C值分布在一个较为稳定的范围内,缅甸琥珀δ13C=-19.38‰-22.90‰,平均值为-21.15‰;波罗的海琥珀δ13C=-22.76‰-25.76‰,平均值为-24.35‰;多米尼加琥珀δ13C=-23.57‰-26.63‰,平均值为-24.99‰,且均值无交叉;(2)不同产地琥珀的δ13C值与琥珀形成的地质时代存在较好的线性关系。具体表征为随着天然树脂石化地质年代(琥珀化程度)的增加,13C值有规律地增大,据此可推断不同产地琥珀成熟度由高到低的相对顺序为缅甸>波罗的海>多米尼加、墨西哥;(3)柯巴树脂的δ13C值为-26.82‰-29.94‰,平均为-28.55‰,比琥珀的明显贫δ13C,依据实验测试统计数据,推荐参考临界值为-27.00‰(+0.18,-3.00),这为界定琥珀与柯巴树脂提供了稳定同位素依据;(4)缅甸琥珀δD=-195.90‰-244.40‰,平均为-226.00‰;波罗的海琥珀δD=-235.90‰-270.10‰,平均为-256.80‰;多米尼加琥珀δD=-202.80‰-239.40‰,平均为-219.90‰;墨西哥琥珀δD=-218.90‰。不同产地琥珀中δD的同位素变异反映了环境水(大气降水)与古纬度之间的变化规律,即随着琥珀产地古纬度的增加,δD逐渐减小;(5)不同产地琥珀在13C-18 O,D-18 O同位素之间及13C,D,18 O同位素在二维图解、三维空间中具有很好的分区性,表明碳、氢、氧稳定同位素综合分析可以示踪琥珀的产地信息。

     

    Abstract: This paper analyzed C, H and O isotopes of amber from Baltic, Dominica, Mexico, Burma, and copals with Stable Isotope Ratio Mass Spectrography (CRMS).Firstly, δ13C of ambers ranges between -19.38‰ and -25.76‰.δ13C of Burman ambers ranges between -19.38‰ and -22.90‰ with an average of -21.15‰.δ13C of Baltic ambers ranges between -22.76‰and -25.76‰ with an average of -24.35‰, and δ13C of Dominican ambers ranges between -23.57‰and -26.63‰ with an average of -24.99‰.Average C isotopes of ambers from those areas are different.Secondly, there is a good linear relation between δ13C of ambers and their formation ages.With the increase in geological ages of natural ambers, 13C of ambers increases regularly.It is thus suggested that maturity degree of ambers (from high to low) is the Burman amber, Baltic amber, Dominican and Maxican amber.Thirdly, δ13C of copals ranges between -26.82‰ and -29.94‰ with an average of -28.55‰.Based on data of experimental analyses, it is suggested that boundary value between amber and copal is -27.00‰ (+0.18, -3.00), which may provide an isotopic evidence to distinguish between amber and copal.Fourthly, δD of Burman ambers ranges between -195.90‰ and -244.40‰ with an average of -222.59‰.δD of Baltic ambers ranges between -235.90‰and -268.60‰ with an average of -253.46‰.δD of Dominican ambers ranges between -203.30‰ and -228.50‰ with an average of -219.05‰, and that of Mexican ambers is -218.90‰.Change inδD of ambers is closely related with latitude of amber formation.That is, with the increase of latitude, δD gradually decreases.Fifthly, two-dimensional space of 13C-18Oisotopes and D-18Oisotopes, and three-dimensional space 13C, D, 18Oisotopes of ambers vary from different producing areas.It is thus suggested that combinations of C, H and O isotopes of ambers can trace producing areas.

     

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