| 中国东部幔源气体同位素地球化学 |
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| 引用本文： | 陶士振,刘德良,朱文锦,杨晓勇.中国东部幔源气体同位素地球化学[J].大地构造与成矿学,2001,25(4):412-419. |
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| 作者姓名： | 陶士振 刘德良 朱文锦 杨晓勇 |
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| 作者单位： | 1. 中国科学技术大学地球与空间科学学院,
2. 山东胜利油田孤东采油厂, |
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| 基金项目： | 国家计委科技攻关项目，96-110 01-06-07， |
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| 摘 要： | 中国东部地幔岩包体及其单矿物中发育有大量的流体包裹体，采用阶段加热真空热爆的 方法脱出幔源包裹体中的气体，测试了气体的碳、氧、氦、氮等同位素组成。ＣＯ２的σ１３℃普遍较低， 主峰值为（－１８～－２２）×１０－3 ，多数样品在高温下的 σ１３℃普遍小于低温下的对应值。氧同位素变 化也很大，从－３．４×１０－３至２５．５×１０－３（ＳＭＯＷ），并呈现多峰的特征。σ１８Ｏ与σ１Ｃ３具有很好的相 关性，可能受控于同种分馏机制。Ｃ、Ｏ同位素组成特征表明，中国东部大陆地幔具有很大的化学不 均一性，可能是由地幔碳的多样性、源区的不均一性或地幔交代作用所致。氧同位素的变化可能是 结晶作用、去气作用或地壳物质混染所至。４Ｈｅ含量变化范围为（０．２４～２５．００）×１０－８，３Ｈｅ／４Ｈｅ变 化范围为（０．４６～１２．８０）×１０－６，４０Ａｒ含量从０．９７×１０－６到３４．１８×１０－６，４０Ａｒ／３６Ａｒ变化范围为 ２５０．５８～１２０２。３Ｈｅ／４Ｈｅ的变化反映了亏损地幔和富集地幔的存在。不同地区４０Ａｒ／３６Ａｒ的巨大差 异显示了地幔脱气程度的不同，也说明在地幔演化中Ａｒ、Ｈｅ同位素地球化学行为的差异。
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| 关 键 词： | 气体同位素 流体包裹体 地幔岩 中国东部 |
| 文章编号： | 1001-1552(2001)04-412-08 |
| 修稿时间： | 2001年7月10日 |
ISOTOPE GEOCHEMISTRY OF MANTLE-DERIVED GAS IN EASTERN CHINA |
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| Abstract: | There are enormous fluid inclusions in the enclave and their single minerals of pyrohte in eastern China. The gases in mantle-derived inclusions were discharged in vacuum state by heating pyrolite samples at different temperature stages. The isotope compositions of carbon, oxygen, helium, argon and the contents of helium, argon were tested respective ly. The σ13Cc02 are very low widespread, concentrating principally between-18×10-3 and -22×103. For most samples, theσ13Cc02 in high temperature are less than that in low temperature. σ18Oco2 varies between-3. 4 ×10-3 and 25. 5×10-3(SMOW), and presents polymodal distribution. σ13C and σ18O of CO2 display obvious correlativity which probably are controlled by same fractionation mechanism. The characteristics of carbon and oxygen isotope indicate that continent mantle possesses considerable chemistry inhomogeneity, which possibly results from the diversity of carbon in mantle, inhomogeneity of origin or mantle metasomatism. Oxygen isotope variation maybe results from crystallization, degasification or hybridization of crust materials. The contents of 4He distribute between 0. 24×10-8 and 25. 00×10-8, 3He/4He changes from 0. 46×10-6 to 12. 80×10-6, 40Ar 0. 9×10-6~34. 18× 10-6, 40Ar/36Ar 250. 58~1202. The variation of 3He/4He discloses the existence of depleted mantle and enriched mantle. Intense difference of 40Ar/36Ar in different area show the difference of degasification degree of mantle. Study result indicates the difference of isotope geochemistry of helium and argon in mantle evolution. |
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| Keywords: | Isotope geochemistry mantle-derived gas fluid inclusion pyrolite eastern China |
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