| 南秦岭元古宙板内火山作用特征及构造意义 |
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| 引用本文： | 徐学义,夏祖春,夏林圻.南秦岭元古宙板内火山作用特征及构造意义[J].岩石矿物学杂志,2001,20(3):255-262. |
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| 作者姓名： | 徐学义 夏祖春 夏林圻 |
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| 作者单位： | 西安地质矿产研究所, |
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| 摘 要： | 南秦岭元古宙火山岩主要由两大类岩石构成，一类为SiO245%-57%的基性火山岩系，另一类为SiO267%-78%的酸性火山岩系，主要岩石类型为细碧岩、玄武岩和石英角班岩、流纹岩。基性火山岩整体上属拉斑玄武岩系列，酸性火山岩属钙碱系列。火山岩强烈富集稀土元素，尤其是轻稀土元素，酸性火山岩和基性火山岩有相似的稀土元素特征，显示了源区特征的不同。基性火山岩富集强不相容元素，相对亏损Nb和Ti, 成于大陆裂谷环境，具有大陆拉斑玄武岩的特征。同位素特征表明基性火山作用与地幔柱活动密切相关。南秦岭的中、晚元古代大陆拉张及由古地幔柱活动所引发的陆裂火山岩浆活动是古秦岭洋打开的先兆。
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| 关 键 词： | 火山岩 元古宙 地球化学 构造背景 南秦岭 板内火山作用 地幔柱 |
| 文章编号： | 1000-6524 (2001) 03-0255-08 |
| 修稿时间： | 2001年4月27日 |
Proterozoic Intraplate Volcanic Rocks in South QinlingMountains and Their Tectonic Implications |
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| XU Xue_yi,XIA Zu_chun,XIA Lin_qi.Proterozoic Intraplate Volcanic Rocks in South QinlingMountains and Their Tectonic Implications[J].Acta Petrologica Et Mineralogica,2001,20(3):255-262. |
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| Authors: | XU Xue_yi XIA Zu_chun XIA Lin_qi |
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| Abstract: | The Proterozoic volcanic rocks in South Qinling are dominated by basic volcanic rocks with SiO245%~57% and acid volcanic rocks with SiO267%~78%. The basic volcanic rocks with spilites and basalts as the major types are close to tholeiite series, whereas the acid rocks with quartz-keratophyre as the major type are close
to calc-alkaline series. Both the basic and the acid volcanic rocks are enriched with REE, especially LREE, indicating that they were derived from different sources. Primitive mantle-normalized trace element patterns of the basic volcanic rocks exhibit the continental tholeiitic characteristics with highly-enriched incompatible elements and moderately-depleted Nb and Ti, suggesting that they were formed in the continental rift. According to the Sr-Nd isotopic study, the basic volcanism was closely related to the mantle plume upwelling. All the features demonstrate that the continental rift in South Qinling region was formed in Middle-Late Proterozoic, and the mantle plume activity was the precursor of the break-up of the ancient Qinling Ocean. |
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| Keywords: | volcanic rock Proterozoic geochemistry tectonic setting South Qinling |
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