| 中国东部碱性花岗岩氢氧同位素特征及其地球动力学意义 |
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| 引用本文： | 魏春生,郑永飞,赵子福.中国东部碱性花岗岩氢氧同位素特征及其地球动力学意义[J].地球物理学报,1998,41(Z1):169-183. |
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| 作者姓名： | 魏春生 郑永飞 赵子福 |
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| 作者单位： | 中国科学技术大学地球与空间科学系,合肥230026 |
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| 基金项目： | 国家自然科学基金,49603043，49453003;中国科学院基金 |
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| 摘 要： | 对中国东部五个有代表性的碱性花岗岩体氢氧同位素研究表明，δ18O基本正常的苏州和福州碱性花岗岩D亏损分别受单阶段与连续岩浆去气作用的影响，后期大气降水的扰动相对较弱．D-18O同步亏损特征明显的碾子山和山海关碱性花岗岩则主要受岩浆期后大气降水高温亚固态同位素交换机理的制约青岛复式花岗岩基则较为复杂，可能受岩浆去气与晚期大气降水交换的联合作用．未明显受后期地质作用扰动、典型的中国东部碱性花岗岩浆氢氧同位素组成分别为δD＝（50±5）‰和δ18＝（7．5±1．0）‰这表明中国东部碱性花岗岩是由稳定同位素组成基本正常的内地壳或上地幔物质通过低程度部分熔融产生的，而不是由再循环亏损源区物质产生的低δ18O岩浆结晶分异形成的．中国东部碱性花岗岩总体上表现出的D亏损纬度效应，预示自中生代以来其所在板块位置未发生过大规模水平位移同时，碱性花岗岩与拉张环境之间的内在联系表明，至少在中生代中国东部大陆岩石圈地壳处于拉张减薄状态．
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| 关 键 词： | 地球动力学 地球化学 氢氧同位素 碱性花岗岩 中国东部 |
| 收稿时间： | 1997-09-09 |
HYDROGEN AND OXYGEN ISOTOPES OF ALKALINE GRANITES DISTRIBUTED ALONG CONTINENTAL MARGINS IN THE EASTERN CHINA AND GEODYNAMIC IMPLICATIONS |
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| WEI CHUN-SHENG,ZHENG YONG-FEI,ZHAO ZI-FU.HYDROGEN AND OXYGEN ISOTOPES OF ALKALINE GRANITES DISTRIBUTED ALONG CONTINENTAL MARGINS IN THE EASTERN CHINA AND GEODYNAMIC IMPLICATIONS[J].Chinese Journal of Geophysics,1998,41(Z1):169-183. |
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| Authors: | WEI CHUN-SHENG ZHENG YONG-FEI ZHAO ZI-FU |
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| Institution: | Department of Earth and Space Sciences, Universiyt of Science and Technology of China,Hefei 230026, China |
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| Abstract: | The hydrogen and oxygen isotopic compositions were investigated for five representative alkaline granite massifs distributed along continental margins in the eastern China. The results show that D depletion of δ18O-normal Suzhou and Fuzhou granite is related to batch and Rayleigh magma outgassing, respectively. Post-magmatic meteoric water pertubation was relatively weak. On the other hand, the synchronous D-18O depletion of Nianzishan and Shanhaiguan granites is mainly ascribable to the subsolidus interaction of external infiltrating meteoric water during magmatic wanning stage. The Qingdao granites would be of complicated evolution history. It's probably subject to both magma degassing and post-magmatic meteoric water isotope exchange. The case study and theoretical consideration illustrate that the hydrogen and oxygen isotopic comopition of the typical alkaline granitic magma, which was not disturbed by late-and post-magmatic processes（e. g., degassing vs water-rock interaction vs AFC, etc）, has δD of （-50±5）‰ and δ18O of （7 .5± 1 .0）‰,respectively. This indicates that the alkaline granites of the eastern China were derived from the partial melting of infracrustal and/or upper mantle source rocks which have the normal stable isotope comopitions rather than from crystallization of recycled low δ18O ,magma. The D-depleted altitude effect of the alkaline grenites in the eastern China implies that their resident plates did not horizontally drift sigificantly. Meanwhile, the essential connection between alkaline granites and extensional tectonic settings demonstrates that the continental lithospheric crust of the eastern China was decompressed and thinned at least during late Mesozoic era. |
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| Keywords: | Geodynamics Hydrogen-oxygen isotopes Alkaline granites Eastern China |
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