| 新疆北部晚古生代埃达克岩、富铌玄武岩组合：古亚洲洋板块南向俯冲的证据 |
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| 引用本文： | 张海祥,牛贺才,Hiroaki Sato,单强,于学元,Jun'ichi Ito,张旗.新疆北部晚古生代埃达克岩、富铌玄武岩组合：古亚洲洋板块南向俯冲的证据[J].高校地质学报,2004,10(1):106-113. |
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| 作者姓名： | 张海祥 牛贺才 Hiroaki Sato 单强 于学元 Jun'ichi Ito 张旗 |
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| 作者单位： | 1. 中国科学院广州地球化学研究所，广州 510640; 2. 日本神户大学理学部地球和行星科学教室，日本神户 657-8501; 3. 中国科学院地质及地球物理研究所，北京 100029 |
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| 基金项目： | 国家自然科学基金 (40 0 73 0 0 6)，国家重点基础研究发展规划 (973 )项目 (2 0 0 1CB40980 5)资助 |
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| 摘 要： | 地球化学研究结果表明，新疆北部富蕴县境内的晚古生代下泥盆统托让格库都克组的安山质岩石具有与埃达克岩非常相似的地球化学特征，它们具有较高的Al2O3，Na2O和Sr含量以及Sr/Y比值；明显亏损重稀土和Y，它们的MORB标准化微量元素蛛网图表现为明显的Nb，Ta负异常和Sr正异常，同时强烈亏损高场强元素。与埃达克岩共生的玄武岩的地球化学特征则与富铌玄武岩一致，表现为Si过饱和及富Na的特征，同时具有较高的Nb，TiO2和P2O5含量，并富集高场强元素。由于埃达克岩和富铌玄武岩的形成均与板块俯冲有关，因此，它们的存在表明，古亚洲洋在早-中泥盆世向南(哈萨克斯坦-准噶尔板块)发生了一次洋壳俯冲作用。
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| 关 键 词： | 哈萨克斯坦-准噶尔板块 埃达克岩和富铌玄武岩 古亚洲洋 板块俯冲 |
| 文章编号： | 1006-7493(2004)01-106-08 |
| 修稿时间： | 2004-03-20 |
Late Paleozoic Adakite and Nb-enriched Basalt from Northern Xinjiang:Evidence for the Southward Subduction of the Paleo-Asian Ocean |
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| ZHANG Hai-xiang,NIU He-cai,Hiroaki Sato,SHAN Qiang,YU Xue-yuan,Jun'ichi Ito,ZHANG Qi.Late Paleozoic Adakite and Nb-enriched Basalt from Northern Xinjiang:Evidence for the Southward Subduction of the Paleo-Asian Ocean[J].Geological Journal of China Universities,2004,10(1):106-113. |
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| Authors: | ZHANG Hai-xiang NIU He-cai Hiroaki Sato SHAN Qiang YU Xue-yuan Jun'ichi Ito ZHANG Qi |
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| Institution: | 1. Guangzhou Institute of Geochemistry, CAS, Guangzhou 510640, China; 2. Department of Earth and Planetary Sciences, Faculty of Science, Kobe University, Kobe 657-8501, Japan; 3. Institute of Geology and Geophysics, CAS, Beijing 100029, China |
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| Abstract: | An adakite and Nb-enriched basalt association is found in early Devonian Group in north Junggar, Xinjiang, northwest China. This association is very important not only for studying the southward subducsion of the Paleo-Asian Ocean, but also provides an ideal research project for evolution of northern margin of the Kazakhstan-Junggar Plate in Late Paleozoic. The geochemical results show that the geochemical characteristics of the andesitic rocks in this area are consistent with those of adakites. They have high Al_2O_3, Na_2O and Sr contents, and high Sr/Y ratio. HREE and Y in the samples are obviously depleted. MORB-normalized trace element spider diagram shows negative Nb, Ta anomalies and remarkably positive Sr anomaly with very strong HFSE depletion. Their chrondrite-normalized REE patterns show no Eu anomaly and HREE depletion. The geochemical features of the associated Nb-enriched basalts are very similar to those of typical Nb-enriched basalts. They are SiO_2 overstraturated and Na-enriched,and are distinguishable from the typical arc basalts which are characteristic of high Nb, Ti, P contents, and HSFE enrichment. The projections of the adakites fall into the mantle array area that is defined by oceanic basalt in the ~ (87) Sr/~(86)Sr vs ~(143) Nd/~(144)Nd diagram. It means that the adakite was derived from the partial melting of the Palaeo-Asian oceanic crust, and the Nb-enriched basalt was originated by the partial melting of the mantle wedge which was slightly contaminated by the continental crust. Because the adakite and Nb-enriched basalt are related with ocean plate subduction, the distribution of the association in northern Junggar indicates that the Palaeo-Asian oceanic crust subducted southwards beneath the Kazakhstan-Junggar Plate in Early Devonian. |
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| Keywords: | Kazakhstan-Junggar Plate Palaeo-Asian ocean adakite and Nb-enriched basalt subduction |
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