| 岩浆去气作用碳硫同位素效应 |
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| 引用本文： | 郑永飞,傅斌.岩浆去气作用碳硫同位素效应[J].地质科学,1996,31(1):43-53. |
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| 作者姓名： | 郑永飞 傅斌 |
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| 作者单位： | 1. 中国科学技术大学地球和空间科学系 合肥 230026;2. 第三世界科学院中国科学技术大学地球科学和天文学高级研究中心 合肥 230026 |
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| 摘 要： | 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着亏损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着亏损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。
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| 关 键 词： | 岩浆 去气作用 碳同位素 硫同位素 火成岩 |
| 收稿时间： | 1994-07-30 |
EFFECTS OF MAGMA DEGASSING ON THE CARBON AND SULFUR ISOTOPE COMPOSITIONS OF IGNEOUS ROCKS |
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| Zheng Yongfei,Fu Bin,Zhang Xuehua.EFFECTS OF MAGMA DEGASSING ON THE CARBON AND SULFUR ISOTOPE COMPOSITIONS OF IGNEOUS ROCKS[J].Chinese Journal of Geology,1996,31(1):43-53. |
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| Authors: | Zheng Yongfei Fu Bin Zhang Xuehua |
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| Institution: | 1. Department of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026;2. Advanced Centre for Earth Sciences and and Astronomy, University of Science and Technology of China,Third World Academy of Sciences, Hefei 230026 |
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| Abstract: | The effect of magma degassing on the carbon and sulfur isotopic compositionsof igneous rocks has been modelled theoretically.All possible dissolved carbon andsulfur species in magmas have been taken into account.The carbon isotopic variations of carbonate and graphite in melts are treated, respectively.So do for the sulfur isotopic variations of sulfate and sulfide.The modelling is based on the principles of Rayleigh distillation in an open system.Assuming the δ13C value of-5 ‰ for the initial magma, the outgassing of CO2 can result in the large negative δ13C values of melt, whereas the outgassing of CH.can drive the δ13C valuesof melt in the positive direction.The theoretical predictions can be used to explainthe fall range of δ13C values from -30 ‰, to + 3 ‰, observed for natural basalts.Likewise, assuming the δ34S value of 0 ‰ for the initial magma, the outgassingof SO2 or H2S can cause the sulfide sulfur in melts to be significantly depleted orenriched in 34S.Therefore, the carbon and sulfur isotopic variations in igneousrocks can be caused by magma degassing instead of the isotopic heterogeneities inprovenace or the contamination of crustal sediments. |
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