| Deep Fractionation of Clinopyroxene in the East Pacific Rise 13 degrees N: Evidence from High MgO MORB and Melt Inclusions | |
| Zhang Guoliang1,2; Zeng Zhigang1; Yin Xuebo1; Wang Xiaoyuan1,2; Chen Daigeng1,2 | |
| 2009 | |
| 发表期刊 | ACTA GEOLOGICA SINICA-ENGLISH EDITION
 |
| ISSN | 1000-9515 |
| 卷号 | 83期号:2页码:266-277 |
| 文章类型 | Article |
| 摘要 | Mid-ocean ridge basalts (MORBs) from East Pacific Rise (EPR) 13 degrees N are analysed for major and trace elements, both of which show a continuous evolving trend. Positive MgO-Al(2)O(3) and negative MgO-Sc relationships manifest the cotectic crystallization of plagioclase and olivine, which exist with the presence of plagioclase and olivine phenocrysts and the absence of clinopyroxene phenocrysts. However, the fractionation of clinopyroxene is proven by the positive correlation of MgO and CaO. Thus, MORB samples are believed to show a "clinopyroxene paradox". The highest magnesium-bearing MORB sample E13-3B (MgO = 9.52%) is modelled for isobaric crystallization with COMAGMAT at different pressures. Observed CaO/Al(2)O(3) ratios can be derived from E13-3B only by fractional crystallization at pressure > 4 +/- 1 kbar, which necessitates clinopyroxene crystallization and is not consistent with cotectic crystallization of olivine plus plagioclase in the magma chamber (at pressure similar to 1 kbar). The initial compositions of the melt inclusions, which could represent potential parental magmas, are reconstructed by correcting for post-entrapment crystallization (PEC). The simulated crystallization of initial melt inclusions also produce observed CaO/Al(2)O(3) ratios only at > 4 +/- 1 kbar, in which clinopyroxene takes part in crystallization. It is suggested that MORB magmas have experienced clinopyroxene fractionation in the lower crust, in and below the Moho transition zone. The MORB magmas have experienced transition from clinopyroxene+plagioclase+olivine crystallization at > 4 +/- 1 kbar to mainly olivine+plagioclase crystallization at < 1 kbar, which contributes to the explanation of the "clinopyroxene paradox".; Mid-ocean ridge basalts (MORBs) from East Pacific Rise (EPR) 13 degrees N are analysed for major and trace elements, both of which show a continuous evolving trend. Positive MgO-Al2O3 and negative MgO-Sc relationships manifest the cotectic crystallization of plagioclase and olivine, which exist with the presence of plagioclase and olivine phenocrysts and the absence of clinopyroxene phenocrysts. However, the fractionation of clinopyroxene is proven by the positive correlation of MgO and CaO. Thus, MORB samples are believed to show a "clinopyroxene paradox". The highest magnesium-bearing MORB sample E13-3B (MgO = 9.52%) is modelled for isobaric crystallization with COMAGMAT at different pressures. Observed CaO/Al2O3 ratios can be derived from E13-3B only by fractional crystallization at pressure > 4 +/- 1 kbar, which necessitates clinopyroxene crystallization and is not consistent with cotectic crystallization of olivine plus plagioclase in the magma chamber (at pressure similar to 1 kbar). The initial compositions of the melt inclusions, which could represent potential parental magmas, are reconstructed by correcting for post-entrapment crystallization (PEC). The simulated crystallization of initial melt inclusions also produce observed CaO/Al2O3 ratios only at > 4 +/- 1 kbar, in which clinopyroxene takes part in crystallization. It is suggested that MORB magmas have experienced clinopyroxene fractionation in the lower crust, in and below the Moho transition zone. The MORB magmas have experienced transition from clinopyroxene+plagioclase+olivine crystallization at > 4 +/- 1 kbar to mainly olivine+plagioclase crystallization at < 1 kbar, which contributes to the explanation of the "clinopyroxene paradox". |
| 关键词 | Mid-ocean Ridge Basalts Primary Magma Fractionation Clinopyroxene Paradox East Pacific Rise |
| 学科领域 | Geosciences, Multidisciplinary |
| DOI | 10.1111/j.1755-6724.2009.00030.x |
| 收录类别 | SCI |
| 语种 | 英语 |
| WOS记录号 | WOS:000265250900010 |
| 引用统计 | |
| 文献类型 | 期刊论文 |
| 条目标识符 | http://ir.qdio.ac.cn/handle/337002/3732 |
| 专题 | 海洋地质与环境重点实验室 |
| 作者单位 | 1.Chinese Acad Sci, Inst Oceanol, Key Lab Marine Geol & Environm, Qingdao 266071, Shandong, Peoples R China 2.Chinese Acad Sci, Grad Sch, Beijing 100049, Peoples R China |
| 第一作者单位 | 中国科学院海洋研究所 |
| 推荐引用方式 GB/T 7714 | Zhang Guoliang,Zeng Zhigang,Yin Xuebo,et al. Deep Fractionation of Clinopyroxene in the East Pacific Rise 13 degrees N: Evidence from High MgO MORB and Melt Inclusions[J]. ACTA GEOLOGICA SINICA-ENGLISH EDITION,2009,83(2):266-277. |
| APA | Zhang Guoliang,Zeng Zhigang,Yin Xuebo,Wang Xiaoyuan,&Chen Daigeng.(2009).Deep Fractionation of Clinopyroxene in the East Pacific Rise 13 degrees N: Evidence from High MgO MORB and Melt Inclusions.ACTA GEOLOGICA SINICA-ENGLISH EDITION,83(2),266-277. |
| MLA | Zhang Guoliang,et al."Deep Fractionation of Clinopyroxene in the East Pacific Rise 13 degrees N: Evidence from High MgO MORB and Melt Inclusions".ACTA GEOLOGICA SINICA-ENGLISH EDITION 83.2(2009):266-277. |
| 条目包含的文件 | ||||||
| 文件名称/大小 | 文献类型 | 版本类型 | 开放类型 | 使用许可 | ||
| zhang-Deep Fractiona（1365KB） | 限制开放 | -- | 浏览 | |||
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
修改评论