| 青藏高原岩石圈演化的记录：藏北超钾质及钠质火山岩的岩石学与地球化学特征 |
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| 作者姓名： | Ding Lin Zhang Jinjiang Zhou Yong DengWanming Xu Ronghua and Zhong Dalai. |
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| 作者单位： | 中国科学院地质研究所,北京,100029 |
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| 基金项目： | 国家重点基础研究专项经费资助,中科院青藏高原研究项目 |
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| 摘 要： | 藏北鱼鳞山超钾质火山岩为一中等规模的熔岩被， 可分为三期。前两期主要为霞石黝方白榴石响岩、霞石白榴斑岩等， 后期主要为方钠石霓石粗面岩、霓霞粗面岩等。时代为１８～３０ Ｍａ。本区超钾质岩浆 Ｓｉ Ｏ２ 强烈不饱和、强碱性、高度富集 Ｌ Ｒ Ｅ Ｅ及 Ｌ Ｉ Ｌ Ｅ、放射成因 Ｓｒ、 Ｐｂ 及非放射成因 Ｎｄ 同位素 （８６ Ｓｒ／８７ Ｓｒ＝ ０７０８７６６～０７０９１６２， ２０６ Ｐｂ／２０４ Ｐｂ＝ １８８８２８８８～ １９１０４７５１， ２０７ Ｐｂ／２０４ Ｐｂ＝ １５６４２０３７ ～ １５８２８４５８， ２０８ Ｐｂ／２０４ Ｐｂ＝ ３９１３８９２１ ～ ３９６８６８３５ 及１４３ Ｎｄ／１４４ Ｎｄ＝ ０５１２１１６ ～０５１２３４２），其上述特征指示岩浆源区为受到地壳物质强烈交代的富集 Ｅ Ｍ Ｉ Ｉ型地幔。藏北拉嘎拉钠质碱性橄榄玄武岩为高原面上的剥蚀残丘， 时代为６０ Ｍａ。其岩石学、 Ｒ Ｅ Ｅ、微量元素及 Ｓｒ Ｎｄ Ｐｂ 同位素指示了岩浆源区为受到洋壳俯冲物质交代的轻度富集地幔。本研究结果指示， 羌塘高原南部富集地幔的形成可能是受到印度板块俯冲的影响。
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| 关 键 词： | 青藏高原 超钾质火山岩 钠质火山岩 岩石学 地球化学 岩石圈演化 |
Tectonic implication on
the lithosphere evolution of the Tibet Plateau |
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| Ding Lin,Zhang Jinjiang,Zhou Yong,DengWanming,Xu Ronghua and Zhong Dalai..Tectonic implication on
the lithosphere evolution of the Tibet Plateau[J].Acta Petrologica Sinica,1999,15(3):86. |
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| Authors: | Ding Lin Zhang Jinjiang Zhou Yong Deng Wanming Xu Ronghua and Zhong Dalai |
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| Abstract: | The Yulinshan is a medium lava sheet, composited of three volcano stages The earlier two period vocanic rocks are majorly nepheline nosean columbretite and nepheline leucitite, and the later are majorly sodalite ponzite and nephelin aegirine trachyte Ages of the volcanic rocks range from 18 to 30Ma The ultrapotassic volcanic magma is highly SiO 2 unsaturated, highly alkaline, highly enriched in LILE, LREE, radiogenic Sr, Pb and unradiogenic Nd( 86 Sr/ 87 Sr= 0 708766 ~0 709162, 206 Pb/ 204 Pb=18 882888~19 104751, 207 Pb/ 204 Pb=15 642037~15 828458, 208 Pb/ 204 Pb=39 138921~39 686835 and 143 Nd/ 144 Nd=0 512116~0 512342)characteristics which suggests an enriched EMII mantle source in which the crust materials are largely involved The Lagala pass sodic alkiline dorgalite is a monadnock of denudation with age of 60Ma The petrology, REE, LILE and Sr Nd Pb isotopes characteristics proposed a lightly enriched mantle source which had experienced ocean crust subduction The results of this study suggest that the formation of the enriched EMII mantle had possibly resulted from the subduction of the India plate crust |
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| Keywords: | Tibet Plateau Ultrapotassic volcanic rocks Sodic volcanic rocks Petrology Geochemistry Lithosphere evolution |
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