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根据开放体系条件下的瑞利分馏原理，并考虑岩浆中可能溶解的合碳和含硫组分，从理论上定量模式了岩浆去气作用对火成岩碳、硫同位素组成的影响。结果表明，岩浆ＣＯ２去气作用能够导致岩石中碳酸盐显著亏损１３Ｃ，其δ１３Ｃ值能够从原始－５‰变化到－２０‰（ＰＤＢ）；岩浆ＣＨ４去气作用则导致岩石中碳酸盐相对富集１３Ｃ，其δ１３Ｃ值能够从原始－５‰变化到＋４‰。岩浆ＳＯ２去气作用可以导致岩石中硫化物显著亏损３４Ｓ，其δ３４Ｓ值能够从０‰变化到－８‰（ＣＤＴ）；岩浆Ｈ２Ｓ去气作用则导致岩石中的硫化物相对富集４Ｓ，其δ３４Ｓ值能够从０‰变化到＋６‰。因此，除源岩原始同位素不均一性和地壳物质混染能引起火成岩的碳、硫同位素组成发生较大变化外，岩浆去气作用也是重要原因之一。
According to the Rayleigh fractionation principle under the open system and taking into account the possible dissolved carbon and sulfur components in the magma, the effect of magma degassing on the carbon and sulfur isotopic composition of igneous rocks is theoretically quantified. The results show that CO2 depletion in the magma can lead to a significant depletion of carbonate in the rock by 13C, and its δ13C value can vary from the original -5 ‰ to -20 ‰ (PDB); the degassing of magma CH4 results in carbonate relative to the rock 13C enrichment, its δ13C value can be changed from the original -5 ‰ to + 4 ‰. The degassing of magma SO2 can lead to a significant depletion of sulfide in rocks by 34S with a δ34S value varying from 0 ‰ to -8 ‰ (CDT). Sulfide depletion by H2S results in relatively sulphide enrichment in rocks by 4S with δ34S The value can vary from 0 ‰ to + 6 ‰. Therefore, in addition to the original isotopic heterogeneity of source rocks and the contamination of crustal materials, the carbon and sulfur isotopic compositions of igneous rocks are greatly changed. The magma degassing is also one of the important reasons.