| 大别-苏鲁超高压变质带榴辉岩部分熔融的证据——微量元素和铅同位素 |
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| 引用本文： | 贾望鲁,高山,等.大别-苏鲁超高压变质带榴辉岩部分熔融的证据——微量元素和铅同位素[J].地球科学,2003,28(2):121-128. |
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| 作者姓名： | 贾望鲁 高山 |
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| 作者单位： | 中国地质大学地球科学学院，湖北武汉430074 |
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| 基金项目： | 国家自然科学基金，国家自然科学基金，49625305，49794043，， |
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| 摘 要： | 俯冲玄武质洋壳的部分熔融作用是一种重要的大陆生长作用，但是陆壳物质在俯冲过程中能否发生部分熔融缺少直接的证据。笔者利用已有的微量元素分配系数，讨论了岛弧玄武岩在脱水和部分熔融2种过程中微量元素行为和铅同位素演化的差异。Pb在2种过程中都属于不相容元素，但在脱水过程中其不相容性明显高于Rb、Ba、Th、U，而在熔融过程中则低于上述元素，在ω(Rb)/ω(Pb)-ω(Rb)、ω（Ba)/ω(Pb)-ω(Ba)、ω（Th)/ω(Pb)-ω(Th)、ω（U）／ω(Pb)-ω(U)相关图上2种过程的演化方向差别明显。此外，Pb和Th、U的相容性的差异也使得石榴石和绿辉石的单矿物铅同位素在2种过程中明显不同。在此基础上，结合大别－苏鲁榴辉岩的实测数据，认为大别－苏鲁榴辉岩可能部分是岛弧玄武岩部分熔融后的残余体，部分为单纯脱水的产物。大陆玄武质岩石在俯冲过程中也可能发生部分熔融作用。
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| 关 键 词： | 超高压变质带 脱水作用 微量元素 铅同位素 榴辉岩 |
| 文章编号： | 1000-2383(2003)02-0121-08 |
Evidence of Partial Melting of Eclogites from Dabie-Sulu Ultrahigh-Pressure Metamorphic Belt: Trace Elements and Pb Isotope |
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| JIA Wang-lu,GAO Shan,WANG Lin-sen,HU Sheng-hong.Evidence of Partial Melting of Eclogites from Dabie-Sulu Ultrahigh-Pressure Metamorphic Belt: Trace Elements and Pb Isotope[J].Earth Science-Journal of China University of Geosciences,2003,28(2):121-128. |
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| Authors: | JIA Wang-lu GAO Shan WANG Lin-sen HU Sheng-hong |
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| Abstract: | Partial melting of subducted oceanic crust is one of the most important processes of continental growth. However, we see little direct evidence of partial melting of the continental during subduction. The difference in trace elements and Pb isotope between dehydration and partial melting of island arc basalt (IAB) is discussed based on the distribution coefficients of trace elements published. Although Pb was incompatible in both dehydration and partial melting, the activity of Pb was higher significantly than other incompatible elements (Rb, Ba, Sr, Th and U) in dehydration, and lower in partial melting. As a result, the evolution pathlous of dehydration and partial melting shows a large difference in the w(Rb)/w(Pb)-w(Rb), w(Ba)/w(Pb)- w(Ba), w(Th)/w(Pb)-w(Th), w(U)/w(Pb)-w(U) figure. Furthermore, the difference of incompatibility among Pb, Th and U leads to a significant distinction of single mineral isotope of garnet and omphacite between dehydration and partial melting. Moreover, the composition of trace elements and Pb isotope of actual measurements and that of analog calculation was compared. Most eclogites from Dabie-Sulu ultrahigh pressure belt might be residual after partial melting of IAB, however, the others were products of dehydration of IAB. Therefore, continental basaltic rocks could also be partially melted during subduction like the oceanic crust. |
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| Keywords: | dehydration partial melting trace element Pb isotope eclogite |
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