摘要
通过对中国东北地区花岗岩类样品的分段加热，探讨了岩石中氮气同位素组成的测定方法，并测定了释放 出的Ｎ_２含量及δ^（１５）Ｎ值。分析结果表明，中国东北不同地区的花岗岩、流纹岩和花岗斑岩在分段加热过程中，不同温 度段释放Ｎ_２含量及其同位素组成特征不同，释放Ｎ_２含量差别较大。花岗岩释放Ｎ_２含量为 １．６４～６．２３μＬ／ｇ，最大 释放峰温度在６００ ℃左右，流纹岩、花岗斑岩释放Ｎ_２含量为 １０８．９８～７５５．９６μＬ／ｇ，最大释放峰温度在 ８００℃左 右。实验结果表明，不同地区岩石中流体性质差异较大，呈现明显的不均一性。对各释放温度段内释放的Ｎ同位素组成加权处理后， Ｎ_２的同位素组成为＋ ９． ２‰＋ １７． ０‰，变化范围达 ７． ８‰，这可能是由于岩浆上升侵入过程中脱气造成同位素分馏，样品加热释放出的流体是脱气后残留的组分。
The determining method of nitrogen isotopic compositions for the granites collected from the northeastern part of China is studied. The content and isotopic values of nitrogen released from the granites by stepwise heating are determined. It's shown that content and isotopic composition released from different area of northeastern China have a great difference. Nitrogen releasing content from granites is 1. 64 - 6. 23 μL/g and the maximum releasing peak is at about 600 ℃, and that from rhyolite and granite-porphyry is 108. 98 - 755. 96 μL/g and the maximum releasing peak is at about 900 ℃. It's proved that liquid characteristic is heterogeneity in the deep crust of the different area in northeastern China. The nitrogen isotopic compositions in different range of temperature are dealed with by weight. The nitrogen isotopic values are + 9. 2‰ to + 17. 0‰, with a changing range of 7. 8‰. The nitrogen ratios maybe have been fractioned during degassing and the releasing component from granites is the residual component.
出处
《地球化学》
CAS
CSCD
北大核心
2000年第2期202-207,共6页
Geochimica
基金
国家自然科学基金!49233060
